JNCIS-SEC Study Guide Part 2
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JNCIS-SEC Study Guide Part 2.
Copyright © 2012, Juniper Networks, Inc.
All rights reserved. Printed in USA.
The information in this document is current as of the date listed above.
The information in this document has been carefully verified and is believed to be accurate for software Release 11.4R1.6. Juniper Networks assumes no
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Contents
Chapter 1: UTM Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1
Chapter 2: Antispam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1
Chapter 3: Full File-Based Antivirus and Express Antivirus . . . . . . . . . . . . . . . . . . . . . . . .3-1
Chapter 4: Content Filtering and Web Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
Contents " iii
Overview
Welcome to the JNCIS-SEC Study Guide Part 2. The purpose of this guide is to help you prepare for
your JN0-332 exam and achieve your JNCIS-SEC credential. The contents of this document are
based on the Junos Unified Threat Management (JUTM) course. This study guide covers Web
filtering, antivirus, antispam, and content filtering. Students will gain experience in configuring and
monitoring the Unified Threat Management (UTM) features of the Junos operating system.
Agenda
Chapter 1: UTM Overview
Chapter 2: Antispam
Chapter 3: Full File-Based Antivirus and Express Antivirus
Chapter 4: Content Filtering and Web Filtering
www.juniper.net iv
Document Conventions
CLI and GUI Text
Frequently throughout this guide, we refer to text that appears in a command-line interface (CLI) or
a graphical user interface (GUI). To make the language of these documents easier to read, we
distinguish GUI and CLI text from chapter text according to the following table.
Style Description Usage Example
Franklin Gothic Normal text. Most of what you read in the Lab Guide
and Student Guide.
Courier New Console text:
commit complete
" Screen captures
" Noncommand-related Exiting configuration mode
syntax
GUI text elements:
Select File > Open, and then click
" Menu names Configuration.conf in the
Filename text box.
" Text field entry
Input Text Versus Output Text
You will also frequently see cases where you must enter input text yourself. Often these instances
will be shown in the context of where you must enter them. We use bold style to distinguish text
that is input versus text that is simply displayed.
Style Description Usage Example
Normal CLI No distinguishing variant. Physical interface:fxp0,
Enabled
Normal GUI
View configuration history by clicking
Configuration > History.
CLI Input Text that you must enter. lab@San_Jose> show route
GUI Input Select File > Save, and type
config.ini in the Filename field.
Defined and Undefined Syntax Variables
Finally, this guide distinguishes between regular text and syntax variables, and it also distinguishes
between syntax variables where the value is already assigned (defined variables) and syntax
variables where you must assign the value (undefined variables). Note that these styles can be
combined with the input style as well.
Style Description Usage Example
CLI Variable Text where variable value is already policy my-peers
assigned.
GUI Variable Click my-peers in the dialog.
CLI Undefined Text where the variable s value is Type set policy policy-name.
the user s discretion or text where
ping 10.0.x.y
the variable s value as shown in
GUI Undefined the lab guide might differ from the Select File > Save, and type
value the user must input filename in the Filename field.
according to the lab topology.
v www.juniper.net
Additional Information
Education Services Offerings
You can obtain information on the latest Education Services offerings, course dates, and class
locations from the World Wide Web by pointing your Web browser to:
http://www.juniper.net/training/education/.
About This Publication
The JNCIS-SEC Study Guide Part 2 was developed and tested using software Release 11.4R1.6.
Previous and later versions of software might behave differently so you should always consult the
documentation and release notes for the version of code you are running before reporting errors.
This document is written and maintained by the Juniper Networks Education Services development
team. Please send questions and suggestions for improvement to [e-mail].
Technical Publications
You can print technical manuals and release notes directly from the Internet in a variety of formats:
" Go to http://www.juniper.net/techpubs/.
" Locate the specific software or hardware release and title you need, and choose the
format in which you want to view or print the document.
Documentation sets and CDs are available through your local Juniper Networks sales office or
account representative.
Juniper Networks Support
For technical support, contact Juniper Networks at http://www.juniper.net/customers/support/, or
at 1-888-314-JTAC (within the United States) or 408-745-2121 (from outside the United States).
www.juniper.net vi
JNCIS-SEC Study Guide Part 2
Chapter 1: UTM Overview
This Chapter Discusses:
" The challenges that branch offices present to network managers;
" The major features of Unified Threat Management (UTM);
" How each major feature addresses the challenges of the branch office;
" The SRX hardware devices on which UTM is available; and
" The UTM features that require specific licenses.
Branch Office Vulnerabilities
A branch office network in today s market significantly contributes to the bottom line and is central to an organization s
success. Branch offices normally include a relatively smaller number of computing resources when compared to central
facilities or headquarters locations. Branch offices are typically located where customer interactions occur, which means there
is increased demand for supporting applications and assuring application performance, an increased demand for security.
General security vulnerabilities exist for every branch office network. These vulnerabilities include spam and phishing attacks,
viruses, trojans and spyware infected files, unapproved website access, and unapproved content.
© 2012 Juniper Networks, Inc. All rights reserved. UTM Overview " Chapter 1 1
JNCIS-SEC Study Guide Part 2
UTM Provides and Enforces Security
UTM security features are provided in the branch SRX devices, enabling a business to protect itself from spam, viruses, worms,
spyware, trojans, and malware. With UTM, you can implement a comprehensive set of security features that include antispam,
antivirus, Web filtering, and content filtering protection. These UTM features provide the ability to prevent threats at the
SRX gateway before the threats enter the network.
UTM Features Are Performed in the Flow Module Services
The graphic shows how traffic is forwarded through the Junos operating system flow module, and at which steps UTM features
are performed. The flow module is integrated into the forwarding path, where the hardware performs data-plane packet
forwarding. The flow module performs UTM features during the services processing. Intelligent packet processing ensures that
one single thread exists for packet flow processing associated with a single flow. Real-time processes enable the Junos OS to
perform session-based packet forwarding. The unified threat management process (UTMD) performs the UTM features and
protects the network from all types of attack. The flowd module and logical packet flow are described in more detail in the JSEC
and AJSEC courses.
Chapter 1 2 " UTM Overview © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
UTM Traffic Processing Overview
The graphic shows UTM traffic processing occurring within the Junos flow module services. As traffic travels inbound on an
interface of the SRX device, security policies process the traffic. If the security policy contains a UTM policy that specifies the
traffic being evaluated, a TCP proxy is used to process the matching traffic. The TCP proxy is used for both a TCP client and TCP
server, to terminate and originate a TCP session. The TCP proxy feeds the data stream to the application proxy. The application
proxy contains a protocol parser, which extracts the application protocol information. The protocol information is evaluated by
the various UTM feature modules.
Antispam
The SRX Series for the branch provides comprehensive UTM features to protect against network-level and application-level
attacks, and simultaneously stops content-based attacks. The antispam feature tags or blocks unwanted e-mail traffic by
scanning inbound and outbound SMTP e-mail traffic.
Antivirus
The antivirus feature uses a scanning engine and virus signature databases to protect against virus-infected files, trojans,
worms, spyware, and other malicious code.
Content Filtering
Content filtering provides basic data loss prevention functionality. Content filtering filters traffic based on MIME type, file
extension, and protocol commands.
Web Filtering
Web filtering is an option that can use either a local Websense server or Internet-based SurfControl server. Web filtering is
critical as a service for tracking productivity and corporate user behavior.
© 2012 Juniper Networks, Inc. All rights reserved. UTM Overview " Chapter 1 3
JNCIS-SEC Study Guide Part 2
Design Considerations
Some UTM features require additional CPU processing, such as antivirus. Available memory and CPU cycles limit the number of
files that can be simultaneously scanned, as well as the size of files that can be scanned. Different antivirus options exist to
accommodate different levels of CPU and memory usage. We discuss antivirus options in more detail in Chapter 4.
Configuration Components
The custom-objects hierarchy level is where you first begin to implement UTM on the SRX device. Custom objects are global
parameters for all UTM features, and are used to create object lists. These object lists contain the building blocks of IP
addresses, domain names, e-mail addresses, URL websites, and so on, used in the different UTM feature profiles. The majority
of UTM settings are configured within the feature profile. The feature profile defines the operation of each UTM feature. For
example, the antivirus feature profile settings control how a protocol is scanned, and what the action will be when spam is
identified. The UTM policy is the central point where all the different feature profiles of UTM are applied. Security policies
reference the UTM policy so that as traffic passes between zones, the SRX device can offer the increased security that UTM
provides.
UTM Policy Flow
The UTM policy within the Junos OS leverages security policies as a central point where traffic is classified and directed to the
appropriate modules for processing. Traffic traversing the security zones of the SRX device are matched against a security
policy. If the security policy contains a UTM policy that matches a protocol supported by UTM, namely SMTP, Post Office Protocol
Chapter 1 4 " UTM Overview © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
3 (POP3) or Internet Message Access Protocol (IMAP), Hyptertext Transfer Protocol (HTTP), or FTP, then the application protocol
data is sent to the UTM feature profile. Each feature profile determines the specific configuration for each feature (antivirus,
content filtering, Web filtering, and antispam).
Display UTM Sessions and Status
The graphic shows the CLI commands to verify UTM
operation. The outputs shown are from an SRX240
device. The show security utm session
command displays general UTM session information
including maximum UTM sessions, allocated UTM
sessions, and active UTM sessions. Any session matching
a security policy with a UTM profile attached and using
one of the protocols configured for UTM (HTTP, IMAP, POP,
SMTP, or FTP) will count as a UTM session. The show
security utm status command displays whether
the UTM service is running.
UTM Hardware Support
UTM features are only supported on high memory branch SRX platforms. You can verify the version (high memory or low
memory) of the SRX device by running the show chassis hardware command. The graphic displays the output for this
command. The chassis description will contain either an H or B after the SRX platform model number. In this case, the output
shows SRX240-H. The H indicates high memory, and the B indicates a base memory (low memory) version. UTM requires the
Junos OS version to be 9.5 or later. The SRX100 does not have a Content Security Accelerator (CSA), which is used with express
antivirus, to improve data throughput performance.
Chassis Cluster Support for UTM Features
UTM functionality is supported in both active/active and active/backup chassis cluster configurations. This feature introduces
UTM support for active/active chassis cluster configurations where the Packet Forwarding Engine (PFE) can be active on both
the cluster nodes. UTM supports stateless PFE active/active chassis cluster configurations, where the UTM state is not
synchronized between the cluster nodes.
© 2012 Juniper Networks, Inc. All rights reserved. UTM Overview " Chapter 1 5
JNCIS-SEC Study Guide Part 2
UTM with chassis cluster supports several failover types:
" Manual failover
" RG0 automatic failover
" RG1+ automatic failover
" Failover through flowd restart
" Failover through reboot
Proxy Server Support for UTM Features
Proxy server support for UTM features is supported on SRX100, SRX210, SRX220, SRX240, SRX650, and all J Series devices. In
certain enterprise networks, the internal network device might not have direct access to the Internet, and the device reaches the
Internet only through a proxy server. The branch SRX devices support UTM feature functionality through a proxy server.
Chapter 1 6 " UTM Overview © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
Licensing
The table illustrates which UTM features require a license.
Verify UTM Licensing
Licenses must be used for successful operation of UTM features. The graphic displays the output of the show system
license command. The output shows the licenses installed for each UTM feature. We cover installation and verification of
UTM licenses in Lab 1.
© 2012 Juniper Networks, Inc. All rights reserved. UTM Overview " Chapter 1 7
JNCIS-SEC Study Guide Part 2
Review Questions
Answers
1.
The four supported features of UTM are antispam, antivirus, Web filtering, and content filtering.
2.
A UTM policy is used to apply a UTM feature profile to application traffic. A security policy is used to evaluate traffic between security
zones of the SRX device. A UTM policy is applied to a security policy.
3.
The UTM features or subfeatures that do not require licensing are content filtering, Websense Web filtering, and local list Web filtering.
Chapter 1 8 " UTM Overview © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
Chapter 2: Antispam
This Chapter Discusses:
" Antispam methods and terminology;
" How Unified Threat Management (UTM) examines traffic for spam;
" The configuration of an effective antispam UTM policy; and
" The verification and monitoring of an antispam operation.
What Is Spam?
Spam consists of unwanted e-mail messages. These e-mail messages are usually sent by commercial, malicious, or fraudulent
entities. Antispam is the ability to prevent spam before it enters the network. Antispam is one of several features including
content filtering, antivirus, and Web filtering that make up Juniper s UTM suite on the SRX Series Services Gateway device.
The antispam feature examines transmitted e-mail messages to identify spam. When the device detects a message deemed to
be spam, it blocks the e-mail message or tags the e-mail message header or subject with a preprogrammed string. Two
methods for performing antispam on the SRX device exist, which we discuss next.
Using an External Spam Block List Server to Identify Spam
The first type of antispam method we discuss is server-based antispam. Server-based antispam means that the SRX device
uses a third-party vendor spam block list (SBL) server over the Internet to identify and eliminate spam. The SBL server uses a
constantly updated, IP-based spam blocking service. It stays current by constantly adding to its IP list of known spammers.
© 2012 Juniper Networks, Inc. All rights reserved. Antispam " Chapter 2 1
JNCIS-SEC Study Guide Part 2
SBL Server Requirements and Restrictions
The SRX device must meet a few requirements to use the SBL server. First, you must have a valid antispam license purchased
and installed on the SRX device (like the licenses you installed during Lab 1).
Also, you must have Internet connectivity with the SBL server. The entry for the third-party SBL server is predefined on the SRX
device, and it is not configurable. Juniper has partnered with a particular vendor (Sophos) to provide server-based antispam
functionality.
Additionally, the Domain Name System (DNS) must be available to access the SBL server. Therefore, a name-server entry
must be properly defined and working on the SRX device. The SRX device performs the SBL lookups through the DNS. The SBL
lookups are performed against the IP address of the e-mail sender or relaying agent. The DNS server then forwards each
request to the SBL server, which returns a DNS response to the SRX device. The SRX device looks at the DNS response to
determine if the e-mail sender is a spammer.
This process automatically occurs when inbound or outbound e-mail traverses the SRX device. You can manually test or query
the SBL server to determine whether an IP address is identified as spam. We discuss this process later in the chapter.
Chapter 2 2 " Antispam © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
Locally Filter IP Addresses, Domain Names, and E-Mail Addresses
The second method of antispam filtering is the use of local lists. This method allows you to manually add an IP address, domain
name entry, or e-mail address to whitelists and blacklists. The SRX device stores and enforces these lists locally. No license is
required for local list spam filtering.
Whitelist
The graphic defines whitelists and blacklists. A whitelist identifies known good e-mail senders that you want the SRX device to
accept. The e-mail messages that match a source on the whitelist are deemed harmless. A match allows the e-mail traffic
through the SRX device.
Blacklist
A blacklist contains the e-mail sources that you want the device to reject. The e-mail messages that match the blacklist are
deemed malicious. A match either blocks the e-mail message or tags the message, depending on the action specified in the
antispam profile configuration. The tag option allows you to configure a message in the e-mail subject line, or in the protocol
header of the packet. When you choose to tag the subject line, a user-defined string is added at the beginning of the subject of
the e-mail. When you choose to tag the header, a user-defined string is added to the protocol header of the packet.
© 2012 Juniper Networks, Inc. All rights reserved. Antispam " Chapter 2 3
JNCIS-SEC Study Guide Part 2
You can configure entries on either list by IP address, e-mail address, or domain name. You can use asterisk * or question mark
? wildcards on the local lists. You must precede all wildcard URLs with http://. You can only use the asterisk * wildcard character
if it is at the beginning of the URL and is followed by a period. You can only use the question mark ? wildcard character at the
end of the URL. The following wildcard syntax is supported: http://*.juniper.net. The following wildcard syntax is not supported:
http://*.
Order of List Checking
The SRX device follows a specific order for checking antispam. The device first checks incoming e-mail against local whitelists
and blacklists. If no match exists on either of these lists, the SRX device queries the SBL server for a match. If a match exists on
any of these lists, the SRX device takes the action depending upon which list was matched, and the default spam action either
blocks or tags.
Order of Match Importance
When configuring the local lists, you should know how the SRX device checks the lists. The sender s IP address is checked first
on the whitelist, and then the blacklist, and then the SBL server. If no matching IP address is found, the device checks for the
sender s domain name on the whitelist, and then the blacklist. If no matching domain name is found, again the device looks for
the sender s e-mail address, again on the whitelist first, and then the blacklist.
On either list, if multiple domain suffixes are configured, the SRX device matches against the longest suffix. For example, if the
sender s e-mail address has a domain name aaa.bbb.ccc, the SRX device looks to match  aaa.bbb.ccc . If no match is found, it
will try to match  bbb.ccc , then  ccc . The SRX device cannot do a partial match against IP addresses. Once a match occurs on
a list, no more matching is processed.
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JNCIS-SEC Study Guide Part 2
SMTP
End users use SMTP to send outbound e-mail, but they do not use SMTP to receive e-mail. On the diagram, User 1 is sending an
e-mail to User 2. The arrows show the path of the e-mail message. SMTP is used to send User 1 s e-mail message to her local
e-mail server. SMTP is again used to relay the message across the Internet to User 2 s local e-mail server. After User 2 s e-mail
server receives the inbound e-mail message, the client connection between User 2 and his local e-mail server synchronizes
through either Post Office Protocol 3 (POP3) or Internet Message Access Protocol (IMAP). This distinction is important because
as of Junos OS Release 11.4, the antispam feature supports filtering only on SMTP. It does not support antispam filtering on
POP3 nor IMAP.
Identifying Spam
Identifying spam means identifying the senders of spam e-mail. The SBL server filters on an IP-based blacklist, and it considers
IP addresses included in the lists to be invalid addresses for mail servers. Criteria must be met to list an e-mail server s IP
address as spam.
The SBL criteria to determine spam includes the following:
" Running an open relay service;
" Running an open proxy (of various kinds);
" Zombie hosts;
" Dynamic IP range (which will unlikely host a mail server); and
" A confirmed spam source (known IPs owned by spammers).
When no positive identification exists for spam on an e-mail message, the e-mail message passes normally.
© 2012 Juniper Networks, Inc. All rights reserved. Antispam " Chapter 2 5
JNCIS-SEC Study Guide Part 2
Handling Identified Spam
Once the SRX device identifies spam, it either blocks or tags the e-mail traffic. Blocked spam is dropped at either the connection
level or e-mail level.
Blocked at the connection level:
" When the SMTP sender is identified as a spam sender based on its IP address or domain name, the SMTP
connection is rejected.
" An error message with a corresponding SMTP error code is sent to close the connection.
Blocked at the e-mail level:
" When the SMTP sender is identified as a spam sender based on its e-mail address, the e-mail is rejected.
" An error message with a corresponding SMTP error code is sent back to the sender.
If the SRX device tags spam at the connection level (based on its IP address or domain name), it tags all e-mails on the
connection. Otherwise, if the SRX device tags spam at the e-mail level, it tags just the individual e-mail message. The SRX device
generates a log message each time it identifies a spam message. The log message contains information about the spam
e-mail s sender, the type of matching spam filter, and what action the SRX device took.
Configuring Antispam
To prevent or reduce the volume of spam messages you receive, you must configure custom objects, an antispam profile, and a
UTM policy.
If you are using local list spam filtering, you must configure whitelists and blacklists under custom objects. If you are using only
server-based spam filtering, you do not have to configure the local lists under custom objects.
The antispam feature-profile is where you apply any local lists that are configured. The feature-profile also
includes the configuration for the default spam action. Note that when you configure the antispam profile, you must either
enable or disable the SBL server.
Next, you create a UTM policy that references the antispam profile. Finally, you assign the UTM policy to a security policy.
Chapter 2 6 " Antispam © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
CLI Antispam Configuration
The graphic examines the command-line
interface (CLI) configuration for the UTM custom
objects and feature profile for antispam. Under
the custom-objects hierarchy, you configure
the local whitelists and blacklists. Remember
the matching order of the entries: by IP address,
then domain name, then e-mail address.
Under the feature-profile hierarchy, you
apply the whitelists and blacklists, as well as
configure the antispam profile settings under
the sbl hierarchy level. After giving the profile a
name (in this case we named the profile
profile1), you can specify to use the SBL
server with the configuration statement
sbl-default-server. If you are not going to
use the SBL server, configure
no-sbl-default-server. You must
configure no-sbl-default-server if you
are only going to use local list filtering.
Next, you specify the spam action, whether it is
block or tag under the spam-action
hierarchy (the command to block is block).
With the spam action tag-subject, you can add a user-defined string the subject line of the e-mail message. With the spam
action tag-header, the user-defined string is added to the e-mail header. You can specify only one tagging action.
Antispam UTM Policy
The graphic demonstrates how to configure the UTM and
security policies.You choose the name for the UTM policy. In
the graphic, the policy is named spam1. Then, under the
anti-spam level of the UTM policy, you specify the
smtp-profile. In this case, the profile is named
profile1. This profile is the SBL profile you created on the
previous graphic, under the feature profile.
Next, apply the UTM policy to the security policy. Be sure to
verify that the security policy is the one referencing the two
correct zones; the first zone is from where the external SMTP
traffic comes, and the second zone is where your SMTP server
is located.
Apply the UTM policy to the appropriate security policy using
the application-services extended permit action, as
demonstrated in the graphic.
© 2012 Juniper Networks, Inc. All rights reserved. Antispam " Chapter 2 7
JNCIS-SEC Study Guide Part 2
J-Web UTM Objects Configuration
This graphic demonstrates how to configure the UTM custom objects using the Junos Web user interface (J-Web). The UTM
configuration is under the security menu on the left side. You begin by configuring the custom objects so that they can be used
in the feature profile and UTM policies.
J-Web Antispam Configuration
The graphic demonstrates how to configure the antispam profile using the J-Web. Note that the custom objects must already be
defined (which is shown in the previous graphic), so that the whitelists and blacklists can be applied to the antispam profile.
The user-defined profile shown in the graphic is named test. When you edit the profile, you can use the default SBL server, or
you can use the default action for identified spam. In this case, the tag-subject option is selected, with the custom tag string
***spam*** to appear in the subject line of the spam e-mail.
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JNCIS-SEC Study Guide Part 2
Notice also that another profile is shown on the screen named junos-as-defaults. This profile is a predefined system
profile, preconfigured with the antispam fallback options. You can view the defaults by using the following operational mode
command:
user@srx> show configuration groups junos-defaults security utm feature-profile
anti-spam
sbl {
profile junos-as-defaults {
sbl-default-server;
spam-action block;
custom-tag-string ***SPAM***;
}
}
Verifying Antispam Operations
The graphic introduces the test command, which you use to determine whether an e-mail sender will be identified as spam.
The command is shown in the graphic.
When an IP address is specified in the test string, the device checks both local whitelists and blacklists, and the SBL server.
With a non-IP address test string (in other words, domain name or an e-mail address), the device checks only the local lists.
Two examples of this command are shown in the graphic. The first command matches an IP address that is configured on the
local blacklist. Note that the returned query value reports the IP address as spam. The second example matches against the
domain name string juniper.net. The string is not matched against any list, and returns a value of NON SPAM.
© 2012 Juniper Networks, Inc. All rights reserved. Antispam " Chapter 2 9
JNCIS-SEC Study Guide Part 2
Monitoring Antispam
The graphic introduces the commands to verify and monitor antispam operation on an SRX device. The first of these commands
shows how many e-mails are scanned, tagged, or dropped:
user@srx> show security utm anti-spam statistics
UTM Anti Spam statistics:
Total connections: 3
Denied connections: 0
Total greetings: 3
Denied greetings: 0
Total e-mail scanned: 3
White list hit: 1
Black list hit: 2
Spam total: 2
Spam tagged: 2
Spam dropped: 0
DNS errors: 0
Timeout errors: 0
Return errors: 0
Invalid parameter errors: 0
Statistics start time: 11/12/2010 16:32:13
Statistics for the last 10 days (permitted emails / spams):
day 1: 1/2
The output shows the total number of e-mail messages, how many hit the whitelist or blacklist, and the total number of spam
messages.
The next show command displays the antispam status for connections, including whitelist and blacklist server information:
user@srx> show security utm anti-spam status
SBL Whitelist Server:
SBL Blacklist Server:
msgsecurity.juniper.net
Chapter 2 10 " Antispam © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
DNS Server:
Primary : 208.67.222.222, Src Interface: ge-0/0/0
Secondary: 0.0.0.0, Src Interface: ge-0/0/8
Ternary : 0.0.0.0, Src Interface: ge-0/0/9
This command is especially helpful when verifying the SBL server status. From the output of this command, we see that the
domain name used to reach the SBL server is msgsecurity.juniper.net, and we see also that the DNS server is specified. The
output of this command also lists the source interface used to reach the DNS server.
In addition, an SRX device creates log messages each time spam is identified. Use the pipe symbol (|) and match option to
display only the antispam log messages.
show log messages | match antispam
The graphic shows two examples of log messages, both reporting that spam has been identified for [e-mail]. The
first log results from the spam action configured as block. When this action is configured, the log message states Deny
reason. The second message results from the spam action configured as tag-subject. When this action is configured, the
log message states Tag email subject reason.
Case Study: Antispam Implementation
The graphic illustrates the topology we use for the next several graphics. To make things simple, we focus on a single, external
domain (xyz.com) to send inbound SMTP traffic through the SRX240 device.
The objectives for this case study are shown on the graphic.
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UTM Configuration
The first part of the UTM configuration is the custom objects. The local whitelist and blacklist have been defined. In this
configuration, the whitelist is named white and the blacklist black. The white list contains the domain name xyz.com. The
black list contains the e-mail address [e-mail]. Because of how the lists are processed, this configuration
accomplishes the objective in the case study. The e-mail address [e-mail] will be blocked, whereas all other e-mails from
xyz.com will be allowed.
The next part of the configuration is the antispam feature-profile. You apply the whitelist and blacklist using the
address-whitelist and address-blacklist commands. You create the antispam feature profile under the [edit
security utm feature-profile anti-spam sbl] hierarchy. This profile allows you to enable the SBL server and
define the default spam action. In this case study, we enable the SBL server and specify the default action to tag the subject line
of the spam e-mail messages.
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UTM and Security Policy Configuration
The graphic shows how to configure and apply the UTM and security policies. In the UTM policy, you must configure an antispam
smtp-profile. This profile is the name of the SBL profile specified on the previous graphic, under the feature-profile
hierarchy for antispam.
Case Study: Name Server Configuration
With the SBL server enabled, you must also configure the name-server (DNS server). The address shown in the example in
the graphic is a public DNS server.
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Case Study: Verifying Antispam Operations
The graphic demonstrates how to test the antispam profile to verify that what we configured on the lists will be properly
matched. The CLI command is specifically testing the string  [e-mail] , which we configured under the blacklist. The
output on the graphic shows that the SRX device identifies the string as spam (because it matched the local blacklist).
Review Questions
Answers
1.
The global UTM configuration elements of antispam are whitelists and blacklists, configured as custom objects.
2.
The match importance order for identifying spam is IP address on the whitelist, IP address on the blacklist, IP address on the SBL server,
domain name on the whitelist, domain name on the blacklist, e-mail address on the whitelist, and e-mail address on the blacklist.
3.
The CLI commands to verify antispam operation are test security utm anti-spam profile profile-name test-string test-string, show security
utm anti-spam status, and show security utm anti-spam statistics.
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JNCIS-SEC Study Guide Part 2
Chapter 3: Full File-Based Antivirus and Express Antivirus
This Chapter Discusses:
" How the antivirus process examines traffic;
" Differences between full file-based and express antivirus;
" Antivirus configuration settings;
" Available scanning options for supported protocols; and
" Verifying antivirus functionality.
What Is a Virus?
A virus is executable code that infects or attaches itself to other executable code to reproduce itself. Malicious viruses erase
files, lock up end host systems, or otherwise interfere with network operation. Other viruses merely infect files and overwhelm
the target host or network with bogus data. Additional virus-related threats include trojans, rootkits, and other types of
malicious code. Viruses are usually spread by attaching themselves as files or scripts inside protocol traffic.
What Is Antivirus?
Antivirus is an established part of the Unified Threat Management (UTM) suite on the Junos operating system, and is an
important part of any enterprise network security strategy. The antivirus feature of the branch SRX gateway prevents viruses at
the gateway before they enter the network. The SRX device uses an antivirus module that includes both a scan engine and a
virus signature database. The antivirus module compares network traffic against known virus types. If a virus is detected, the
file is dropped, and the originator of the traffic is notified. Antivirus scanning is a separately licensed subscription service.
When your antivirus license key expires, you can continue to use locally stored antivirus signatures without any updates. But in
that case, if the local database is deleted, antivirus scanning is disabled. Administrators can choose between two different
types of antivirus scanning methods. Only one type of scanning method can be applied at a time.
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Full File-Based Antivirus Scanning
The first scanning method we discuss is full file-based antivirus scanning. Juniper Networks has partnered with Kaspersky Lab
to provide both the full file-based scan engine and the virus signature database. The full file-based antivirus scan engine
inspects Application Layer data streams, searching for attached files in e-mail messages, Hypertext Transfer Protocol (HTTP)
traffic, and FTP downloads or FTP uploads. This scanning method also searches for embedded scripts when downloading HTTP
Web pages. For the SRX device to scan FTP traffic, the FTP ALG must be enabled.
When the scan engine flags a file or script for inspection, it collects received data packets until it has reconstructed the original
application content, such as an e-mail file attachment, or embedded script. The scan engine caches the file (or script) in
memory and compares it against the virus signature database for a match. Full file-based antivirus scanning has a high
virus-detection rate, and protects against all types of viruses and malicious code, even polymorphic or metamorphic viruses.
These viruses can change themselves. The diagram on the graphic shows how the entire file is received and reconstructed
before virus scanning begins. This process is CPU intensive. Available memory and CPU cycles limit the number of files that can
be simultaneously scanned, as well as the size of files that can be scanned.
Express Antivirus Scanning
The second antivirus scanning method is express antivirus scanning. Express antivirus is a less CPU-intensive alternative to the
full file-based antivirus feature. The express antivirus feature, like the full file-based antivirus feature, scans specific Application
Layer traffic for viruses against a virus signature database. However, unlike full file-based antivirus, express antivirus does not
reconstruct the original application content. Express scanning begins to scan data packets as they are received. With express
antivirus, the virus scanning is executed by a hardware pattern-matching engine. This improves performance while scanning is
occurring, but decreases the level of security provided. Express antivirus uses a different signature database than the full
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JNCIS-SEC Study Guide Part 2
file-based antivirus signature database. The express signature database targets only critical viruses and malware, including
worms, trojans, and spyware. The database is smaller in size, and provides less coverage than the full file-based antivirus
signature database. Express antivirus does not protect against polymorphic or metamorphic viruses, because these viruses can
change themselves. The engine utilizes pattern recognition only and does not use other heuristics to detect these types of
viruses. The diagram on the graphic shows file scanning occurring as the file is received, reducing overall data throughput
latency.
Sophos Live Antimalware Protection
Sophos antivirus scanning is offered as a less CPU-intensive alternative to the full file-based antivirus feature. Sophos supports
the same protocols as full file-based antivirus and functions in much the same manner; however, it has a smaller memory
footprint and is compatible with lower end devices that have less memory. The virus pattern and malware database is located
on external servers maintained by Sophos Extensible List (SXL) servers, thus there is no need to download and maintain large
pattern databases on the Juniper device. The Sophos antivirus scanner also uses a local internal scanner library cache to
maintain query responses from the SXL server to improve lookup performance. Queries are performed using the DNS protocol.
Because a significant amount of traffic processed by the SRX is HTTP based, Uniform Resource Identifier (URI) checking is used
to effectively prevent malicious content from reaching the endpoint client or server. The following checks are performed for
HTTP traffic: URI lookup, true file type detection, and file checksum lookup. The following application layer protocols are
supported: HTTP, FTP, SMTP, POP3 and IMAP. Sophos Antivirus has the following main features:
" Sophos Antivirus Expanded MIME Decoding Support: Sophos antivirus offers decoding support for HTTP, POP3,
SMTP, and IMAP. MIME decoding support includes the following for each supported protocol:
 Multipart and nested header decoding
 Base64 decoding, printed quote decoding, and encoded word decoding in the subject field
" Sophos URI Checking: Sophos provides URI checking, which is similar to antispam realtime blackhole list (RBL)
lookups. URI checking is a way of analyzing URI content in HTTP traffic against the Sophos database to identify
malware or malicious content. Because malware is predominantly static, a checksum mechanism is used to
identify malware to improve performance. Files that are capable of using a checksum include: .exe, .zip, .rar, .swf,
.pdf, and .ole2 (doc and xls).
Pattern Matching
The antivirus module for full file-based and express antivirus contains a database with virus signature patterns. The SRX device
checks files against the database for a match. This process is known as pattern matching. Both full file-based scanning and
express scanning perform pattern matching against a virus signature database, but in different ways. Full file-based antivirus
software pattern matching is where the CPU is responsible for performing the task of pattern matching. The express antivirus
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scanning engine offloads the pattern-matching operation to a hardware engine, the Content Security Accelerator (CSA), which
significantly reduces CPU and memory usage. The CSA hardware engine is available on the SRX210, SRX220, SRX240, and
SRX650 platforms, and yields higher data throughput performance at the expense of somewhat lower catch rates. Platforms not
equipped with a CSA can still perform software pattern matching, but performance will be lower (UTM always requires the
high-memory option).
Pattern Updates
The virus database must stay current to continually match against new virus threats. Pattern update options are used for either
full file-based or express scanning to allow control of the antivirus engine and signature database updates. To manually update
the virus signature database, specify the URL of the database server. If you do not specify a URL, a default URL is provided,
http://update.juniper-updates.net/AV. We discuss the pattern update configuration later in the chapter. The antivirus and
malware database for Sophos antivirus is stored on SXL servers.
Sophos maintains these servers, so there is no need to download and maintain large pattern databases on the SRX device.
Because the database is remote, there is no size limitation and there is a quicker response to new virus outbreaks. Sophos
antivirus uses a set of data files that must be updated on a regular basis. These are not typical virus pattern files; they are a set
of small files that help guide virus scanning logic. You can manually download the data files or set up an automatic download.
Intelligent Prescreening
One technique used to increase the effectiveness of antivirus scanning is intelligent prescreening. Full file-based scanning
begins to scan data after the SRX device has received all the packets of a file. Express scanning begins to scan data packets as
they are received, but still scans all the packets of the file. Intelligent prescreening tells the antivirus scan engine to use the first
packet or the first several packets of a file to determine if the file could possibly contain malicious code. The scan engine does a
quick check on these first packets. If it finds that the file is unlikely infected, then the file is safe to bypass the normal scanning
procedure. It is not necessary to store and scan the whole file. Intelligent prescreening behaves the same for both full file-based
and express antivirus scanning. By default, intelligent prescreening is enabled to improve antivirus scanning performance. You
can disable it with the following command:
set security utm feature-profile anti-virus
kaspersky-lab-engine|juniper-express-engine profile profile-name scan-options
no-intelligent-prescreening
SRX Antivirus Module
The antivirus module is the software subsystem on the SRX device that scans specific Application Layer traffic to protect users
from virus attacks and prevent viruses from spreading. The antivirus module analyzes traffic and sends data to a scan engine
for virus scanning. The software subsystem consists of an application proxy, a scan manager, a scan engine and a virus
signature database. A client establishes a TCP connection with a server and then starts a transaction. If the antivirus module is
interested in the application protocol used, the traffic will be forwarded to the application proxy and the traffic gets parsed for
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attached files. The scan manager monitors the antivirus sessions and checks the properties of data content against the
antivirus settings. If a scan request is sent out, the scan engine scans the data and queries the virus signature database. After
scanning, the result is handled by the scan manager.
Full File-Based Scanning
The graphic shows the full file-based antivirus flow process. The scan engine for this process is provided by Kaspersky Lab, as
well as the virus signature database. When scanning is enabled, TCP data packets come into the SRX device and are handled by
the TCP proxy. The protocol parser inspects HTTP, e-mail, and FTP data streams, searching for attached files or embedded
scripts. Scripts can be found when downloading Web pages. When the protocol parser flags a file for inspection, it caches the
file (or embedded script) in memory to reassemble the original application content, and uses the scanning engine to search for
viruses, trojans, rootkits, and other types of malicious code. If a virus is detected, the file is dropped immediately, and the
sender of the traffic is notified. If no virus is found the traffic is forwarded through the SRX device.
Express Antivirus Flow Process
The graphics demonstrates the express antivirus flow process. Express antivirus uses a modified version of the Kaspersky
signature database. Express antivirus catch rates are lower than full file-based antivirus, but express antivirus is able to catch
the most common viruses. The main advantage that express antivirus provides is higher throughput, as processing is hardware
accelerated. Files are not locally stored, and packets can be inspected as they are forwarded through the SRX device. Packets
still have to go through a TCP proxy and data buffer because TCP streams must be reassembled and packets must be reordered.
Express antivirus minimizes transfer delays because packets can be forwarded while virus scanning is taking place.
Global Antivirus Settings
The antivirus module has global, policy-based, and profile-based settings. Global settings are general overall configurations for
the antivirus module or settings that are not specific to an antivirus profile. Global antivirus settings include UTM custom
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objects, where you can configure whitelists for specific HTTP traffic to bypass antivirus scanning. We discuss the operation and
configuration of these lists later in the chapter.
Policy-Based Antivirus Settings
Policy-based antivirus settings are configured through UTM policies. UTM policies control which protocol traffic is sent to the
antivirus scanning engine. The UTM policy has antivirus profiles for FTP, HTTP, POP3, SMTP, and IMAP traffic. The UTM policy is
applied to a security policy, which determines if the protocol of a traffic flow matches the antivirus profile. If the protocol traffic
matches, it is sent to the antivirus module for virus scanning.
Profile-Based Antivirus Settings
The majority of antivirus settings are configured within the antivirus feature profile. Profile-based antivirus settings control how
each protocol is scanned within the antivirus module. The antivirus feature profile settings include the scanning options, such
as scan type, scan mode, content size limits, scanning timeout values, session throttling, and settings for scanning compressed
files. The feature profile settings also define fallback and notification options.
Scan Mode All
The scanning options for full file-based scanning allow you to configure one of two different scan modes: all or
by-extension. When the scan mode is set to all, the antivirus scanning engine scans every file regardless of the file
extension. The diagram on the graphic shows both inbound and outbound traffic passing different file types through an SRX240.
Each of the file types shown are process for antivirus scanning.
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Scan Mode By-Extension
The diagram on the graphic shows an SRX240 using the by-extension scan mode. In this mode, the SRX device bases all
scanning decisions on the traffic s file extension. Only files that have a file extension matching the extension list are scanned. In
the diagram, the local user sends a file with an extension XSLT, which does not match the file extension list, and is not scanned
by antivirus. The SRX device has a default file extension list already preconfigured. To view the list, run the command shown in
the graphic.
You cannot modify the default file extension list. However, you can configure a custom filename extension list to be used instead
of the default list. We demonstrate the configuration for a custom filename extension list later in the chapter. If a file s extension
is not found on an extension list, the file is not scanned. If the file has no extension, the file is scanned for viruses.
Scanning Compressed Files
The graphic shows additional full file-based scanning options. The SRX antivirus feature supports compressed data detection, in
case a virus is sent inside compressed data. Three kinds of compressed data exist: a compressed file (zip, rar, gzip), encoded
data such as Multipurpose Internet Mail Extension (MIME), and packaged data (OLE, CAP, MSI, TAR, EML). As the virus signature
database becomes larger and the scan algorithms become more sophisticated, the scan engine has the ability to look deeper
into the data for embedded malware. As a result, it can uncover more layers of compressed data. Scanning compressed files is
only supported for HTTP and POP3 traffic. Some files can be compressed multiple times. The SRX antivirus feature will
decompress layers of files until it reaches either a user-configured decompress limit, or the device decompress layer limit,
based on memory allocation. If a file exceeds the compression layer limit, the scan engine either drops or forwards the file
based on the configured fallback options.
Content Size Limits
Antivirus requires the contents of files to be stored in memory to scan files for viruses. Due to resource constraints, a default
device-dependent limit exists on the maximum content size for a file. The content size usually refers to file size, according to the
content length field of the protocol header, or content size refers to the accumulated TCP payload size of the received packets.
The limit for maximum content size is user-configurable. If a file exceeds the content size limit, the scan engine either drops or
forwards the file based on the configured fallback options.
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Scanning Timeout Values
The SRX device can use a scanning timeout value for files that take too long to scan. The timeout value covers the time duration
from when the scan request is generated to when the scan result is returned by the scan engine. The range is 1 to 1800
seconds. By default, it is 180 seconds. It is a parameter used in all protocols and each protocol can have a different value.
Session Throttling
Session throttling restricts the amount of traffic a single source can consume at one time. The limit is an integer with 100 as the
default setting. This integer refers to the maximum allowed sessions from a single source. You can change this default limit, but
understand that if this limit is set high, the setting is comparable to no limit.
HTTP Antivirus Scanning Example
You can turn antivirus scanning on and off on a per protocol basis. If scanning for a protocol is disabled in an antivirus profile, no
application intelligence exists for this protocol, and in most cases, traffic using the protocol is not scanned. But if the protocol in
question is based on another protocol for which scanning is enabled in an antivirus profile, then the traffic is scanned as that
enabled protocol. The internal antivirus scan engine supports scanning for specific Application Layer transactions allowing you
to select the content (HTTP, FTP, SMTP, POP3, or IMAP traffic) to scan.
The graphic shows a general example of how HTTP traffic is intercepted and scanned. Host-A sends an HTTP request to a
webserver. The SRX antivirus module intercepts the request, and parses the protocol for files or scripts. When a file or script is
identified, the data is passed to the antivirus scanner, which scans the data for viruses. After completing the scan, the antivirus
scan engine follows one of two courses. If no virus is detected, the device forwards the request to the webserver. If a virus is
detected, the device drops the request and sends an HTTP message reporting the infection to the client. Antivirus scanning is
supported for HTTP GET, POST (includes HTTP upload), and PUT methods. RFC 2616 is the reference for these protocol
methods. HTTP 1.0 and 1.1 are supported.
HTTP trickling is a time-based mechanism used to prevent the HTTP client or HTTP server from timing-out during antivirus
scanning. HTTP trickling forwards unscanned HTTP traffic to the requesting HTTP client to prevent the browser window from
timing out while the scan manager examines downloaded HTTP files. The SRX device forwards small amounts of data in
advance of transferring an entire scanned file. By default, trickling is disabled. HTTP trickling is only supported for HTTP
connections.
Sophos Live Protection Example
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The graphic demonstrates an example of Sophos live antimalware protection.
Antivirus Whitelists
When the SRX antivirus module parses traffic, it can identify file types that are not considered harmful and should not be
scanned. HTTP MIME headers and URL information can be used to obtain information about the file type being carried. The URL
whitelist is used in the Web filtering UTM feature, where URLs or IP addresses are always not scanned. The URL whitelist
specifies traffic that can bypass antivirus scanning. The SRX device also uses MIME types to decide which traffic can bypass
antivirus scanning. The graphic shows the order of HTTP processing with regards to antivirus scanning. URL whitelists are
matched against first, followed by MIME whitelists. If no match occurs on either whitelist, the antivirus feature profile settings
are followed for virus scanning. The URL and MIME whitelists are only valid for HTTP traffic.
Blocking and Notifications
When the scan engine detects a virus, the file is blocked. Notification options inform users of detected viruses. Different
notification types are available. One option is the notification type message. When content is blocked with the notification type
message, the application client still gets a successful response code, but with modified content containing a warning message.
The warning message can be custom defined. With the notification type protocol-only message, a protocol-specific error code
might be returned to the client, so that the client knows something happened, rather than assuming that the protocol transfer
succeeded. For HTTP and FTP traffic, notifications are piggybacked in the protocols. For example, if a virus is found while doing
an HTTP request, users will see a custom error message on the page they are trying to access. E-mail notifications for SMTP,
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IMAP, and POP3 protocols generate an error mail message, notifying the mail recipient (and optionally the sender) of the
offending mail. Three different settings exist for e-mail notifications:
" Virus-detection/notify-mail-sender: When enabled, this e-mail notifies the sender when a virus is detected.
" Fallback-block/notify-mail-sender: When enabled, this e-mail notifies the sender when other scan-codes or
scanning errors are returned and a message is dropped.
" Fallback-non-block/notify-mail-recipient: When enabled, this e-mail notifies the recipient when other scan-codes or
scanning errors are returned and the message is passed.
Scanning Fallback Options
Fallback options specify the actions to take when traffic cannot be scanned. The fallback actions are to either block, or
log-and-permit. Traffic cannot be scanned because of special conditions:
" Content-size: If the content size exceeds a set limit, the content is passed or blocked depending on the
max-content-size fallback option. The default action is BLOCK.
" Corrupt-file: Corrupt file is the error returned by the scan engine when engine detects a corrupted file. The default
action is PASS.
" Decompress-layer: Decompress layer error is the error returned by the scan engine when the scanned file has too
many compression layers. The default action is BLOCK.
" Default: All the errors other than those in the above list fall into this category. This could include either unhandled
system exceptions (internal errors) or other unknown errors. The default action is BLOCK.
" Engine-not-ready: The scan engine is initializing itself, for example, loading the signature database. During this
phase, it is not ready to scan a file. A file could either pass or be blocked according to this setting. The default
action is BLOCK.
" Out-of-resources: Virus scanning requires a great deal of memory and CPU resources. Due to resource constraints,
memory allocation requests can be denied by the system. This failure could be returned by either scan engine (as a
scan-code) or scan manager. When out-of-resources occurs, scanning is aborted. The default action is BLOCK.
" Password-file: Password protected file is the error returned by the scan engine when the scanned file is protected
by a password. The default action is PASS.
" Timeout: Scanning a complex file could consume resources and time. If the time it is taking to scan exceeds the
timeout setting in the antivirus profile, the processing is aborted and the content is passed or blocked without
completing the virus checking. The decision is made based on the timeout fallback option. The default action is
BLOCK.
Too-many-requests: If the total number of messages received concurrently exceeds the device limits, the content is passed or
blocked depending on the too-many-request fallback option. The default action is BLOCK. (The allowed request limit is not
configurable.)
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UTM Custom Objects Configuration
The UTM custom-objects hierarchy contains global antivirus configuration settings. You can configure URL and MIME
whitelists, and a filename extension list. The filename extension list is used in by-extension scan mode for full file-based
antivirus. The extension list adds additional file extensions to the default list of extensions to be scanned. The graphic shows the
configuration for the URL whitelist, MIME whitelist, and filename extension list. The url-pattern name hierarchy defines the
pattern list name, and value contains the entries for URLs that bypass antivirus scanning. The pattern name is applied to the
custom-url-category value hierarchy level.
The MIME whitelist consists of one or many MIME type entries. The MIME entry is case-insensitive. If the MIME entry ends with
a '/' character, a prefix match is used. Otherwise, exact match is used. Two types of MIME lists exist, a MIME whitelist and a
MIME exception list. The MIME whitelist is used for bypassing antivirus scanning. The MIME exception list is used for excluding
some MIME types from the MIME whitelist. For example, if the MIME whitelist has video/ configured, and the exception list
has video/x-shockwave-flash configured, traffic with MIME type video/ bypasses antivirus scanning, but traffic with
MIME type video/x-shockwave-flash does not bypass antivirus scanning.
The filename extension list contains value entries for file extensions that you want to add to the default file extension list. The
filename extension list, MIME list, exception list, and custom URL category are all applied to the antivirus feature profile.
Automatic Update Configuration
Updates to the pattern file are added as new viruses are discovered. The default antivirus pattern-update interval is 60 minutes.
When Kaspersky Lab updates the signatures in its pattern database, the SRX device downloads these updates so that the
antivirus scanner is using the most current signature database when scanning traffic. The process of downloading updates is
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the same for both full file-based antivirus and express antivirus protection. The graphic shows the configuration for pattern
updates within the antivirus feature profile.
Manually Force an Update
The security device can perform these updates automatically (the default), or you can manually perform a pattern update using
the CLI command shown in the graphic.
To verify that the pattern update is successful, run the show security utm anti-virus status command. We review
the output of this command later in the chapter.
Fallback and Notification Options Configuration
The graphic shows the configuration for the fallback and notification options for full file-based and express antivirus. These
settings are configured under the antivirus profile. The following fail mode options are supported for Sophos antivirus:
content-size, default, engine-not-ready, out-of-resource, timeout, and too-many-requests. The fallback options are taken when
traffic is unable to be scanned, and all fallback options have an action of either block or log-and-permit. The notification
options can be configured for fallback-block, fallback-non-block, or virus-detection.You can configure a
custom notification message for all three options. You can specify the notification type of message or protocol-only for
fallback-block and virus-detection options only.
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Apply the Antivirus Profile to a UTM Policy
UTM policies control which protocol traffic is sent to the antivirus scanning engine. The UTM policy shown ingraphic the graphic
is named policy1, and has the antivirus profile av-profile applied for FTP download and HTTP traffic. Therefore, any FTP
download or HTTP traffic that passes where the UTM policy is applied is processed by the antivirus module, and follows the
settings defined in the antivirus profile.
Apply the UTM Policy to a Security Policy
The graphic configuration shows the UTM policy policy1 applied to the security policy client-to-server. This policy is
looked at for all traffic that passes between the client and server zones of the SRX device.
Verifying Pattern Updates
The output of the show security utm anti-virus status command displays the update server path, the pattern
update status, and last result, as shown in the graphic. If the pattern update is successful, the last result will show that either a
new database has been loaded, or that the SRX device already has the latest database. When the pattern update is successful,
the scan engine is ready. If the pattern update is not successful, the scan engine is not ready, and the fallback option
engine-not-ready action is used.
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Verify Licensing
A license must be used for successful antivirus operation. The top of the graphic shows the output for the show system
license command. The output shows which licenses have been installed. In this case, it shows that the
av_key_kaspersky_engine license has been successfully installed. If the SRX device does not have a license for antivirus, the
show security utm anti-virus status command will display that a license is not installed.
Antivirus Scan Results
The show security utm anti-virus statistics command displays antivirus statistics for connections including
clean files, infected files, and scan engine status. It also shows statistics for traffic that has matched any of the fallback options.
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JNCIS-SEC Study Guide Part 2
Antivirus Log Messages
The graphic demonstrates how to match against the log messages to view if any viruses have been detected. Each time a virus
is detected, the SRX device logs a message, indicating the source and destination addresses, the file name, and the source
zone of the traffic.
Review Questions
Answers
1.
The two full file-based scan mode types are all and by-extension. The difference is that scan mode all scans every file regardless
of the file extension, and scan mode by-extension only scans files matching the extension list.
2.
The methods available for HTTP traffic to bypass antivirus scanning are URL and MIME whitelists. They are defined under UTM custom
objects.
3.
Intelligent prescreening improves scanning performance by eliminating the need to store and scan the entire file. It uses the first packet or
the first several packets of a file to determine if the file could possibly contain malicious code.
© 2012 Juniper Networks, Inc. All rights reserved. Full File-Based Antivirus and Express Antivirus " Chapter 3 15
JNCIS-SEC Study Guide Part 2
Chapter 4: Content Filtering and Web Filtering
This Chapter Discusses:
" The purpose of content filtering and Web filtering;
" The parameters used to configure content filtering and Web filtering;
" Configuring content filtering and Web filtering; and,
" Monitoring content filtering and Web filtering.
Content Filtering
Content filtering is a feature that allows or blocks traffic based on the Multipurpose Internet Mail Extension (MIME) type,
file extension, protocol commands, and embedded object type. This feature is supported for HTTP, FTP, and mail
protocols such as SMTP, Post Office Protocol 3 (POP3), and Internet Message Access Protocol (IMAP).
Once content is blocked, users can be notified by a custom message or e-mail depending on the protocol.
This feature does not require a license.
Traffic Is Permitted Base on Parameters
Content filtering permits or blocks traffic based on the following parameters:
" MIME pattern: Identifies the type of traffic in HTTP and mail protocols.
" File extension: Identifies the type of traffic by file type.
" Protocol command: Identifies the type of commands protocols use. Using FTP as an example, the protocol
commands are the commands between the FTP client and server, not the commands you type when using FTP.
The following list are protocol command examples for the supported protocols:
 HTTP: GET, HEAD, POST, PUT, DELETE, TRACE, OPTIONS, OTHERS
 FTP: USER, PASS, ACCT, CWD, CDUP,SMNT, REIN, QUIT, PORT, PASV
 SMTP: HELO, EHLO, MAIL, RCPT, DATA, SIZE, QUIT, VRFY, EXPN
 POP3: APOP, DELE, LIST, NOOP, PASS, QUIT, RETR, RSET, STAT, TOP, UIDL, USER
 IMAP: CAPABILITY, NOOP, LOGOUT, AUTHENTICATE, LOGIN, SELECT, EXAMINE
Supported Protocols are HTTP, FTP, and Mail Protocols
HTTP supports all the content filtering attributes which includes MIME patterns, file extensions, and protocol commands. HTTP
traffic can also be blocked based on ActiveX, Java applet, cookies, EXE files, and ZIP files. The content filter checks every HTTP
request between client and server. If the content filter is configured to block the request using the protocol command list, it
drops the request and sends back a page with an explanation. If the request is to download a file, it checks the response
header for MIME type and file extension. The content filter also checks the file header for ActiveX and Java applet, and drops
the response if any of them are configured in the blocked content.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 1
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FTP supports the content filtering attributes file extensions and protocol commands. The content filter checks each command,
and drops the command if it is configured in the protocol list or the file extension list. If the command is dropped, it sends back
to the client the custom block message and the reason why. Content filtering support for FTP requires enabling the FTP ALG.
Mail protocols support the content filtering attributes MIME patterns, file extensions, and protocol commands. Content filtering
has a limited ability with MIME type and file extensions. Only one level of the e-mail header is scanned, which means recursive
e-mail headers are not checked along with any encrypted attachments. Also, if the whole e-mail is MIME encoded, only the
mime type is checked. The content filter checks each command, and drops the command if it is configured in the protocol list or
the file extension list. If the command is dropped, It sends back an error code to the client with the explanation.
Users Can Be Notified of Blocked Content in Two Ways
A message embedded in the protocol can be sent to the user, or an e-mail message can be sent. In both cases, the
content of the message is configured by the administrator.
Content Filtering Configuration Options
A content filter must coincide with a list of custom objects, which is a list of objects you would like to allow or block. The one
exception is with HTTP traffic, which can be configured to block content directly under the content filter.
This graphic lists all the configuration options available for custom objects and content filtering.
Custom objects options have the following configuration options:
" MIME pattern: This option enables the creation of a list that can be used for allowing or blocking MIME types. If the
MIME pattern ends with a  / (as an example, video/), prefix matching takes place. If the MIME pattern does not
end with a  / , exact matching occurs.
" Filename extension: This option enables the creation of a list for blocking file extensions.
" Protocol command: This option enables the creation of a list that can be used for allowing or blocking protocol
commands. The protocol commands are checked using a case-insensitive string comparison.
Content filtering has the following configuration options:
" Block or permit command: The block-command list indicates the commands that are blocked, and the
permit-command list has been designed as an exception list. If a command exists in the permit-command list,
it will not be blocked, even if it exists in the block-command list. Commands that do not exist in the
permit-command list will be allowed provided that they also do not exist in the block-command list.
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JNCIS-SEC Study Guide Part 2
" Block extension: Allows you to apply the custom object filename-extension to block files based on the
extension. You can also configure the predefined extension list junos-default-extension. Issue show
groups junos-defaults security utm custom-objects to view predefined custom objects.
" Block MIME: As shown in the graphic provided, you can create a list to block MIME type video/, but allow video/
quicktime. The block-mine exception list has a higher priority than block-mime list. You can also configure the
predefined MIME list junos-default-bypass-mime.
" Block content type: You can also block files based on ActiveX, Java applet, cookies, EXE or ZIP file type. The
block-content-type configuration is for HTTP use only.
" Notification options: Allows for the creation of a custom message sent to the client when traffic is blocked.
Content Filtering Configuration
After you have created a content filtering profile, you create a UTM policy and apply the content filtering profile to the appropriate
traffic you are filtering. The content filtering profile can be applied to multiple protocols. The final step is to apply the UTM policy
to the appropriate security policy.
The graphic shows the options available for applying the content filtering profile and where the UTM policy is applied to the
security policy.
Content Filtering Example for HTTP
This graphic illustrates the topology for this example. The next page shows the content filtering configuration steps to block
downloading ZIP files using HTTP.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 3
JNCIS-SEC Study Guide Part 2
Configuring Content Filtering
The graphic shows the steps for configuring a content filter.
1. Configure the content filtering profile to block ZIP files for HTTP, with a custom message to be displayed in the
webpage.
2. Apply the content filtering profile to the UTM policy, under http-profile.
3. Finally, apply the UTM policy to the appropriate security policy using the application-services extended
permit action.
Verify That Content Filtering Is Working
This graphic shows what the client would see in the Web browser after trying to download a ZIP file.
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JNCIS-SEC Study Guide Part 2
Verify and Monitor Using CLI
The syslog messages logs permitted and blocked content, and the show security utm content-filtering
statistics command counts how many times a custom object or HTTP blocked content has been blocked. The syslog
messages must be configured with a severity of any or info.
Verify and Monitor Using J-Web
The Junos Web user interface (J-Web) provides the same monitoring options as the CLI, and provides further statistics and
graphs to display the blocked traffic.
Web Filtering
Web filtering or URL filtering provides the ability to permit or deny access to specific URLs based on the category to which
they belong. The Web filter intercepts HTTP requests, and a decision is then made with the HTTP request on an external server
(SurfControl or Websense), or on the SRX device (whitelist or blacklist) to permit or block the request.
Web filtering acts as a first line of defense. If a website is a known source of malware, what is easier than blocking access
to that site?
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 5
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The supported three deployment options:
" SurfControl: This option uses an in-the-cloud server which keeps a database of categories for websites.
" Websense: This option uses a locally administrated server which keeps a database of categories and Web filtering
policies.
" Local lists: This option uses configured whitelists and blacklists on the SRX device.
Once traffic has been blocked, the client can receive a custom message in the Web browser.
Junos Has Four Solutions to Web Filtering
The first and most common Web filtering method is to use the in-the-cloud or Internet SurfControl server. The SurfControl
server stores a database of about 40 categories and associated URLs. The integrated SurfControl option requires the
purchase of a Juniper Web filtering license.
The second option is the use of a local Websense server that must be purchased and managed locally. The Websense
server maintains a database of categories and Web filtering policies. The Websense redirect option does not require a
Juniper Web filtering license.
The third option is the use of local URL blacklists and whitelists. The local lists can be used in conjunction with the SurfControl
or Websense option.
The fourth option is to use enhanced Web filtering. Enhanced Web filtering uses an Internet Websense server that stores a
database of over 95 categories and associated site reputation information. The enhanced Web filtering option requires the
purchase of a Juniper Web filtering license.
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SurfControl Integrated Web Filtering Solution
The SurfControl server stores a database of categories and associated URLs. Every time a user tries to access a site, the
SRX device captures the requested URL and queries the SurfControl database. The server responds with the category of
the website, which is used by a Web filtering policy on the SRX device to allow or deny access. The SRX device
generates a log message indicating the action taken. If the action taken was to deny access, a custom message can be
sent to the user. Once a site is associated with a category, the result is cached locally. Subsequent requests for the same
URL do not require a new query to the centralized database. The main advantage of this solution is that users do not need
to host the database, which often requires a redundant server infrastructure.
The SurfControl database features:
" More than 26 million URLs;
" Approximately 40 categories; and
" More than 70 languages.
Websense Redirect Web Filtering Solution
The Websense redirect solution does not require a separate Juniper license, but utilizes a local database, which must be
purchased separately from Websense. As opposed to querying the SurfControl server, the SRX device redirects the URL
to the local Websense server. The Websense server contains both the category database and the Web filtering policies.
The Websense server then compares the URL against its database and returns the result according to its configured
policy. The response is then forwarded to the SRX device indicating whether the URL is allowed or denied.
The Websense redirect server features:
" 95 categories;
" Support for over 100 protocols;
" Local policy evaluation; and
" Logging and reporting support.
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This solution has the advantage of minimizing processing delays because the database is locally stored. The
disadvantages are an administrator to keep the database current and multiple servers if you want redundancy.
Local Blacklists and Whitelists
You can also configure custom URL categories, which can be included in blacklists and whitelists that are evaluated on
the SRX device. All URLs for each category in a blacklist are denied, while all URLs for each category in a whitelist are
permitted. The processing order is as follows:
1. A new URL is first compared to the blacklist URLs. If a match is found, the traffic is dropped without any
further processing.
2. If no match is found, the URL is evaluated against the whitelist, where traffic is allowed if a match is found.
3. If no user defined category results in a match, processing continues either by SurfControl or Websense.
Enhanced Web Filtering
Enhanced Web filtering uses an Internet Websense server that stores a database of more than 95 predefined categories
and associated site reputation information. The enhanced Web filtering option requires the purchase of a Juniper Web
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JNCIS-SEC Study Guide Part 2
filtering license. Enhanced Web filtering intercepts HTTP and HTTPS requests and sends the HTTP URL or the HTTPS
source IP to the Websense ThreatSeeker Cloud (TSC) server. The TSC server categorizes the URL into one of the
predefined categories and obtains site reputation information. The TSC server returns the URL category and the site
reputation information to the SRX device. The SRX device determines if it can permit or block the request based on the
information provided by the TSC, and the feature profile configuration. Enhanced Web filtering supports the following
HTTP methods:
" GET
" POST
" OPTIONS
" HEAD
" PUT
" DELETE
" TRACE
" CONNECT
The graphic demonstrates an example of how HTTP or HTTPS traffic is intercepted, scanned, and acted upon by the
enhanced Web filtering solution. The SRX device makes a TCP socket connection to the TSC server. The SRX device
intercepts an HTTP or HTTPS client connection and extracts each URL in the HTTP request or the IP address in the
HTTPS request. The SRX device verifies whether the URL is in the user-configured blacklist or whitelist. If the URL is in
the user-configured blacklist, the device blocks the URL. If the URL is in the user-configured whitelist, the device permits
the URL. If no match against the local lists exists, the SRX device queries the TSC server for a URL category lookup. The
TSC server responds with the URL category and site reputation information. The SRX device queries the user-defined
categories in the feature profile, and blocks or permits the URL based on the user-specified action for the category.
SurfControl Configuration Options
This graphic illustrates the configuration options available for SurfControl Web filtering.
The SurfControl options are:
" Type: This option allows you to configure the type of Web filtering you are using. SurfControl is the default Web
filtering type.
" Cache: This option allows you to configure the size and duration of the cache. The cache is used for the URL
categories from the SurfControl server.
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" Server: This option allows you to configure the host or address, and port of the SurfControl server. A server host or
address is required.
" Category: This option allows you to permit or block URLs based on the category with which the SurfControl server
responds. You can also permit or block any custom categories you configure.
" Default: This option allows you to configure a default permit or block action. If a URL does not match a category, the
URL is either permitted or blocked. If the default option is not configured, the URL is permitted.
" Custom block message: This option allows you to configure a custom message. The message will be seen by the
client when a URL is blocked.
This list is a continuation of the SurfControl options on the preceding page:
" Fallback settings: This option allows you to permit or block URLs during the following error conditions:
 Default: Default error condition;
 Server connectivity: No connectivity to the Web filter server;
 Timeout: A Web filter request times out; and
 Too many requests: There are too many concurrent requests.
" Timeout: This option allows you to configure the timeout value in seconds, after which a request is considered to
have timed out.
Websense Configuration Options
The graphic illustrates the configuration options available for Websense Web filtering.
The Websense options are:
" Type: This option allows you to configure the type of Web filtering you are using. Websense must be configured or
SurfControl will be used.
" Server: This option allows you configure the host or address, and port of the Websense server.
" Custom block message: This option allows you to configure a custom message. The message will be seen by the
client when a URL is blocked.
" Fallback settings: This option allows you to permit or block URLs during error conditions. The error conditions
configuration options are the same as SurfControl.
" Timeout: This option allows you to configure the timeout value in seconds, after which a request is considered to
have timed out.
Chapter 4 10 " Content Filtering and Web Filtering © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
" Sockets: This option allows you to configure the number of persistent sockets to be opened to the Websense
server.
" Account: This option allows you to configure the Websense server account.
Local Blacklist and Whitelist Options
Local Web filtering by default permits all URLs, therefore a URL pattern to allow URLs is not needed. You only need to configure
a whitelist if you configure the default action to block under the juniper-local profile. The Web filtering type must be
configured for juniper-local, or the default Web filtering SurfControl will be used. You must configure a URL pattern for
the websites you want to block, and apply the URL pattern to a custom URL category. The custom URL category is then applied
under the web-filtering hierarchy as a url-blacklist to block the URL. You can also configure the same custom
message and fallback options as previously mentioned.
The graphic shows how the URL pattern is associated with the custom URL category, and how the custom URL category
associates with the Web filter.
The Web Filter Must be Applied
The Web filtering profile must be applied to a UTM policy and the UTM policy must be applied to the appropriate security policy.
The graphic shows where the Web filtering profile is applied to the UTM policy, and where the UTM policy is applied to the
security policy.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 11
JNCIS-SEC Study Guide Part 2
Custom Objects Configuration
The first step to configuring enhanced Web filtering is to create any custom objects to be applied to the enhanced Web filtering
feature profile. In the example, we create a URL pattern list called urllist3 that contains the pattern values
http://www.juniper.net and 1.2.3.4. The urllist3 custom object is then added to the custom URL category
custurl3. The graphic also demonstrates URL pattern lists for trusted and untrusted sites called urllistwhite and
urllistblack.The URL pattern lists are applied to the custom-objects custom-url-category lists called custwhitelist and
custblacklist.
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JNCIS-SEC Study Guide Part 2
Apply Custom Objects to the Feature Profile
The next step is to configure the global options for the enhanced Web filtering feature profile. By default the, the enhanced Web
filtering profile name is named junos-wf-enhanced-default. The graphicexample shows the custom object
custwhitelist applied to the URL whitelist, and the custom object custblacklist applied to the URL blacklist. The type
of Web filtering engine for enhanced Web filtering is Juniper-Enhanced. Then you set the cache size and cache timeout
parameters. Configure the Enhanced Web Filtering server as rp.cloud.threatseeker.com . Configure the TCP port
number for communicating with it. The default port number is 80.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 13
JNCIS-SEC Study Guide Part 2
Configure the Feature Profile URL Categories and Site Reputation
Next, edit the enhanced Web filtering feature profile and navigate to the URL category action list tab. Select a category from the
included whitelist and blacklist categories or select a custom URL category list you created for filtering against. Configure each
category with an action of permit, log and permit, or block. The example blocks URLs in the Enhanced_Gambling category,
but logs and permits URLs in the Enhanced_Hacking category. You also specify the action to be taken depending on the site
reputation returned for the URL if there is no category match found. You can configure a custom message to be sent when HTTP
requests are blocked. The graphic also shows the site reputation actions you can configure for each URL.
Chapter 4 14 " Content Filtering and Web Filtering © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
Apply the UTM Policy to the Security Policy
The last step is to create a UTM policy that references the enhanced Web Filtering feature profile. In the example, the UTM policy
is named junos-wf-policy. The graphic shows the UTM policy being applied under the application services tab of the
security policy.
Local Web Filtering
This graphic illustrates the topology for this example. The next few pages show the Web filtering configuration steps to block
access to a bad website.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 15
JNCIS-SEC Study Guide Part 2
Configuring Custom URL Patterns and Categories
The graphic illustrates configuring URL patterns and applying the URL pattern to a custom URL category.
Configuring the Web Filter Profile
The graphic shows applying the custom URL categories under the Web filter, and creating a local profile with a custom block
message. The URL whitelist and blacklist can be used with other Web filtering solutions, such as SurfControl.
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JNCIS-SEC Study Guide Part 2
Applying the Policies
The graphic shows where the Web filtering profile is applied to the UTM policy, and where the UTM policy is applied to the
security policy.
You can also apply predefined Web filtering profiles to the UTM policy. To view the predefined Web filtering profiles, issue the
show group junos-defaults security utm feature-profile web-filtering command.
The following output shows the Web filtering UTM policy options:
user@srx# set utm-policy policy1 web-filtering http-profile ?
Possible completions:
Web-filtering HTTP profile
block-bad [security utm feature-profile web-filtering juniper-local
profile]
junos-wf-cpa-default [security utm feature-profile web-filtering
surf-control-integrated profile]
junos-wf-local-default [security utm feature-profile web-filtering juniper-local
profile]
junos-wf-websense-default [security utm feature-profile web-filtering
websense-redirect profile]
Verify That Web Filtering Is Working
The graphic shows what the client would see in the Web browser after trying to access a blocked website.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 17
JNCIS-SEC Study Guide Part 2
Verify and Monitor Using CLI
The syslog messages log permitted or blocked content, and the show security utm web-filtering statistics
command counts how many times a URL was permitted or blocked. The syslog messages must be configured with a severity of
any or info.
Verify and Monitor Using J-Web
J-Web provides the same monitoring options as CLI, and also provides further statistics and graphs to display the blocked traffic.
Chapter 4 18 " Content Filtering and Web Filtering © 2012 Juniper Networks, Inc. All rights reserved.
JNCIS-SEC Study Guide Part 2
Review Questions
Answers
1.
The Junos OS supports the file extension and protocol command content filtering attributes.
2.
The three Web filtering solutions are SurfControl, Websense, and local whitelist and blacklist.
3.
The Web filtering solution SurfControl requires a Juniper license.
© 2012 Juniper Networks, Inc. All rights reserved. Content Filtering and Web Filtering " Chapter 4 19