PIX/ASA 7.x and Later: Block the Peer-to-Peer (P2P) and Instant Messaging (IM) Traffic Using MPF Configuration Example

Introduction

This document describes how to configure the Cisco Security Appliances PIX/ASA using Modular Policy Framework (MPF) in order to block the Peer-to-Peer (P2P) and Instant Messaging (IM), such as MSN Messenger and Yahoo Messenger, traffic from the inside network to the Internet. Also, this document provides information on how to configure the PIX/ASA in order to allow the two hosts to use IM applications while the rest of the hosts remain blocked.

Prerequisites

Requirements

This document assumes that Cisco Security Appliance is configured and works properly.

Components Used

The information in this document is based on the Cisco 5500 Series Adaptive Security Appliance (ASA) that runs software version 7.0 and later.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Related Products

This configuration can also be used with the Cisco 500 Series PIX firewall that runs software version 7.0 and later.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Modular Policy Framework Overview

MPF provides a consistent and flexible way to configure security appliance features. For example, you can use MPF to create a timeout configuration that is specific to a particular TCP application, as opposed to one that applies to all TCP applications.

MPF supports these features:

  • TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number randomization

  • CSC

  • Application inspection

  • IPS

  • QoS input policing

  • QoS output policing

  • QoS priority queue

The configuration of the MPF consists of four tasks:

  1. Identify the Layer 3 and 4 traffic to which you want to apply actions. Refer to Identifying Traffic Using a Layer 3/4 Class Map for more information.

  2. (Application inspection only) Define special actions for application inspection traffic. Refer to Configuring Special Actions for Application Inspections for more information.

  3. Apply actions to the Layer 3 and 4 traffic. Refer to Defining Actions Using a Layer 3/4 Policy Map for more information.

  4. Activate the actions on an interface. Refer to Applying a Layer 3/4 Policy to an Interface Using a Service Policy for more information.

Configure the P2P and IM Traffic Blocking

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool ( registered customers only) to obtain more information on the commands used in this section.

Network Diagram

This document uses this network setup:

pixasa-imblock-config1.gif

PIX/ASA 7.0 and 7.1 Configuration

Block the P2P & IM Traffic Configuration for PIX/ASA 7.0 and 7.1 

CiscoASA#show run
: Saved
:
ASA Version 7.1(1)
!
hostname CiscoASA
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!


!--- Output Suppressed



http-map inbound_http
content-length min 100 max 2000 action reset log
content-type-verification match-req-rsp action reset log
max-header-length request 100 action reset log
max-uri-length 100 action reset log
port-misuse p2p action drop
port-misuse im action drop
port-misuse default action allow


!--- The http-map "inbound_http" inspects the http traffic
!--- as per various parameters such as content length, header length,
!--- url-length as well as matches the P2P & IM traffic and drops them.


!


!--- Output Suppressed


!
class-map inspection_default
match default-inspection-traffic
class-map http-port
match port tcp eq www


!--- The class map "http-port" matches
!--- the http traffic which uses the port 80.


!
!
policy-map global_policy
class inspection_default
 inspect dns maximum-length 512
 inspect ftp
 inspect h323 h225
 inspect h323 ras
 inspect netbios
 inspect rsh
 inspect rtsp
 inspect skinny
 inspect esmtp
 inspect sqlnet
 inspect sunrpc
 inspect tftp
 inspect sip
 inspect xdmcp
policy-map inbound_policy
class http-port
 inspect http inbound_http


!--- The policy map "inbound_policy" matches
!--- the http traffic using the class map "http-port"
!--- and drops the IM traffic as per http map
!--- "inbound_http" inspection.


!
service-policy global_policy global
service-policy inbound_policy interface inside


!--- Apply the policy map "inbound_policy"
!--- to the inside interface.


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CiscoASA#

Refer to the Configuring an HTTP Map for Additional Inspection Control section of the Cisco Security Appliance Command Line Configuration Guide for more information about the http map command and various parameters associated with it.

PIX/ASA 7.2 and Later Configuration

Note: The http-map command is deprecated from software version 7.2 and later. Therefore, you need to use the policy-map type inspect im command in order to block the IM traffic.

Block the P2P & IM Traffic Configuration for PIX/ASA 7.2 and Later

 
CiscoASA#show running-config
: Saved
:
ASA Version 8.0(2)
!
hostname pixfirewall
enable password 8Ry2YjIyt7RRXU24 encrypted
names



!--- Output Suppressed


class-map inspection_default
match default-inspection-traffic
class-map imblock
match any


!--- The class map "imblock" matches
!--- all kinds of traffic.


class-map P2P
match port tcp eq www


!--- The class map "P2P" matches
!--- http traffic.


!
policy-map type inspect dns preset_dns_map
parameters
 message-length maximum 512

policy-map type inspect im impolicy
parameters
match protocol msn-im yahoo-im
 drop-connection



!--- The policy map "impolicy" drops the IM
!--- traffic such as msn-im and yahoo-im .


policy-map type inspect http P2P_HTTP
parameters
match request uri regex _default_gator
 drop-connection log
match request uri regex _default_x-kazaa-network
 drop-connection log


!--- The policy map "P2P_HTTP" drops the P2P
!--- traffic that matches the some built-in reg exp's.






policy-map IM_P2P
class imblock
 inspect im impolicy
class P2P
 inspect http P2P_HTTP 



!--- The policy map "IM_P2P" drops the
!--- IM traffic matched by the class map "imblock" as
well as P2P traffic matched by class map "P2P".


policy-map global_policy
class inspection_default
 inspect dns preset_dns_map
 inspect ftp
 inspect h323 h225
 inspect h323 ras
 inspect netbios
 inspect rsh
 inspect rtsp
 inspect skinny
 inspect esmtp
 inspect sqlnet
 inspect sunrpc
 inspect tftp
 inspect sip
 inspect xdmcp
!
service-policy global_policy global
service-policy IM_P2P interface inside


!--- Apply the policy map "IM_P2P"
!--- to the inside interface.


prompt hostname context
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CiscoASA#

List of built-in regular expressions

 
regex _default_GoToMyPC-tunnel "machinekey"
regex _default_GoToMyPC-tunnel_2 "[/\\]erc[/\\]Poll"
regex _default_yahoo-messenger "YMSG"
regex _default_httport-tunnel "photo[.]exectech[-]va[.]com"
regex _default_gnu-http-tunnel_uri "[/\\]index[.]html"
regex _default_firethru-tunnel_1 "firethru[.]com"
regex _default_gator "Gator"
regex _default_firethru-tunnel_2 "[/\\]cgi[-]bin[/\\]proxy"
regex _default_shoutcast-tunneling-protocol "1"
regex _default_http-tunnel "[/\\]HT_PortLog.aspx"
regex _default_x-kazaa-network "[xX]-[kK][aA][zZ][aA][aA]-[nN][eE][tT][wW][oO][rR][kK]"
regex _default_msn-messenger "[Aa][Pp][Pp][Ll][Ii][Cc][Aa][Tt][Ii][Oo][Nn][/\\][Xx][-][Mm][Ss][Nn][-]
[Mm][Ee][Ss][Ss][Ee][Nn][Gg][Ee][Rr]"
regex _default_aim-messenger "[Hh][Tt][Tt][Pp][.][Pp][Rr][Oo][Xx][Yy][.][Ii][Cc][Qq][.][Cc][Oo][Mm]"
regex _default_gnu-http-tunnel_arg "crap"
regex _default_icy-metadata "[iI][cC][yY]-[mM][eE][tT][aA][dD][aA][tT][aA]"
regex _default_windows-media-player-tunnel "NSPlayer"

PIX/ASA 7.2 and Later: Allow the Two Hosts to Use the IM Traffic

This section uses this network setup:

pixasa-imblock-config2.gif

Note: The IP addressing schemes used in this configuration are not legally routable on the Internet. These are RFC 1918 addresses, which have been used in a lab environment.

If you want to allow the IM traffic from the specific number of the hosts, then you need to complete this configuration as shown. In this example, the two hosts 10.1.1.5 and 10.1.1.10 from the inside network are allowed to use the IM applications such as MSN Messenger and Yahoo Messenger. However, the IM traffic from other hosts is still not allowed.

IM Traffic Configuration for PIX/ASA 7.2 and Later to Allow Two Hosts 

CiscoASA#show running-config
: Saved
:
ASA Version 8.0(2)
!
hostname pixfirewall
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface Ethernet0
nameif inside
security-level 100
ip address 10.1.1.1 255.255.255.0
!
interface Ethernet1
nameif outside
security-level 0
ip address 192.168.1.1 255.255.255.0
!


!--- Output Suppressed



passwd 2KFQnbNIdI.2KYOU encrypted
ftp mode passive

access-list 101 extended deny ip host 10.1.1.5 any
access-list 101 extended deny ip host 10.1.1.10 any
access-list 101 extended permit ip any any


!--- The ACL statement 101 is meant for deny the IP
!--- traffic from the hosts 10.1.1.5 and 10.1.1.10
!--- whereas it allows the rest of the hosts.


pager lines 24
mtu inside 1500
mtu outside 1500
no failover
icmp unreachable rate-limit 1 burst-size 1
no asdm history enable
arp timeout 14400
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect
timeout uauth 0:05:00 absolute
dynamic-access-policy-record DfltAccessPolicy
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
no crypto isakmp nat-traversal
telnet timeout 5
ssh timeout 5
console timeout 0
threat-detection basic-threat
threat-detection statistics access-list
!
class-map type inspect im match-all im-traffic
match protocol msn-im yahoo-im


!--- The class map "im-traffic" matches all the IM traffic
!--- such as msn-im and yahoo-im.



class-map im_inspection
match access-list 101


!--- The class map "im_inspection" matches the access list
!--- number 101.


class-map inspection_default
match default-inspection-traffic
!
!
policy-map type inspect dns preset_dns_map
parameters
 message-length maximum 512
policy-map global_policy
class inspection_default
 inspect dns preset_dns_map
 inspect ftp
 inspect h323 h225
 inspect h323 ras
 inspect netbios
 inspect rsh
 inspect rtsp
 inspect skinny
 inspect esmtp
 inspect sqlnet
 inspect sunrpc
 inspect tftp
 inspect sip
 inspect xdmcp
policy-map type inspect im im-policy
parameters
class im-traffic
 drop-connection log


!--- The policy map "im-policy" drops and logs the
!--- IM traffic such as msn-im and yahoo-im.



policy-map impol
class im_inspection
 inspect im im-policy


!--- The policy map "impol" inspects the IM traffic
!--- as per traffic matched by the class map "im_inspection".
!--- So, it allows the IM traffic from the host 10.1.1.5
!--- and 10.1.1.10 whereas it blocks from rest.


!
service-policy global_policy global
service-policy impol interface inside


!--- Apply the policy map "impol" to the inside
!--- interface.


prompt hostname context
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Verify

Use this section to confirm that your configuration works properly.

The Output Interpreter Tool ( registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

  • show running-config http-map—Shows the HTTP maps that have been configured.

    CiscoASA#show running-config http-map http-policy
    !
    http-map http-policy
    content-length min 100 max 2000 action reset log
    content-type-verification match-req-rsp reset log
    max-header-length request bytes 100 action log reset
    max-uri-length 100 action reset log
    !

  • show running-config policy-map—Displays all the policy-map configurations as well as the default policy-map configuration.

    CiscoASA#show running-config policy-map
    !
    policy-map type inspect dns preset_dns_map
    parameters
     message-length maximum 512
    policy-map type inspect im impolicy
    parameters
    match protocol msn-im yahoo-im
     drop-connection
    policy-map imdrop
    class imblock
     inspect im impolicy
    policy-map global_policy
    class inspection_default
     inspect dns preset_dns_map
     inspect ftp
     inspect h323 h225
     inspect h323 ras
     inspect netbios
     inspect rsh
     inspect rtsp
     inspect skinny
     inspect esmtp
     inspect sqlnet
     inspect sunrpc
     inspect tftp
     inspect sip
     inspect xdmcp

    You can also use the options in this command as shown here:

    show running-config [all] policy-map [policy_map_name |
    type inspect [protocol]]
    CiscoASA#show running-config policy-map type inspect im
    !
    policy-map type inspect im impolicy
    parameters
    match protocol msn-im yahoo-im
     drop-connection
    !

  • show running-config class-map—Displays the information about the class map configuration.

    CiscoASA#show running-config class-map
    !
    class-map inspection_default
    match default-inspection-traffic
    class-map imblock
    match any

  • show running-config service-policy—Displays all currently running service policy configurations.

    CiscoASA#show running-config service-policy
    service-policy global_policy global
    service-policy imdrop interface outside

  • show running-config access-list—Displays the access-list configuration that is running on the security appliance.

    CiscoASA#show running-config access-list
    access-list 101 extended deny ip host 10.1.1.5 any
    access-list 101 extended deny ip host 10.1.1.10 any
    access-list 101 extended permit ip any any

Troubleshoot

This section provides information you can use to troubleshoot your configuration.

Note: Refer to Important Information on Debug Commands before you use debug commands.

  • debug im—Shows the debug messages for IM traffic.

  • show service-policy—Displays the configured service policies.

    CiscoASA#show service-policy interface outside

    Interface outside:
     Service-policy: imdrop
       Class-map: imblock
         Inspect: im impolicy, packet 0, drop 0, reset-drop 0

  • show access-list—Displays the counters for an access list.

    CiscoASA#show access-list
    access-list cached ACL log flows: total 0, denied 0 (deny-flow-max 4096)
               alert-interval 300
    access-list 101; 3 elements
    access-list 101 line 1 extended deny ip host 10.1.1.5 any (hitcnt=0) 0x7ef4dfbc
    access-list 101 line 2 extended deny ip host 10.1.1.10 any (hitcnt=0) 0x32a50197
    access-list 101 line 3 extended permit ip any any (hitcnt=0) 0x28676dfa
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