Applied Mitigation Bulletin

IPS signature event data from Cisco Remote Management Services is available for IPS signatures from August 19, 2010.

Contents

Introduction

Microsoft announced 14 security bulletins that contain 34 vulnerabilities as part of the monthly security bulletin release on August 10, 2010. A summary of these bulletins is on the Microsoft website at http://www.microsoft.com/technet/security/bulletin/ms10-aug.mspx. This document highlights the vulnerabilities that can be effectively identified and/or mitigated using Cisco network devices.

The vulnerabilities that have a client software attack vector, or can be exploited locally on the vulnerable device, or require user interaction or can be exploited using web-based attacks (these include but are not limited to cross-site scripting, phishing, and web-based e-mail threats), and e-mail attachments are in the following list:

• MS10-047
• MS10-048
• MS10-049
• MS10-050
• MS10-051
• MS10-052
• MS10-053
• MS10-055
• MS10-056
• MS10-057
• MS10-058
• MS10-059
• MS10-060

The vulnerabilities that have a network mitigation are in the following list. Cisco devices provide several countermeasures for the vulnerabilities that have a network attack vector, which will be discussed in detail later in this document.

• MS10-050
• MS10-051
• MS10-054
• MS10-055
• MS10-060

Information about affected and unaffected products is available in the respective Microsoft advisories and the IntelliShield alerts that are referenced in the following table. In addition, multiple Cisco products use Microsoft operating systems as their base operating system. Cisco products that may be affected by the vulnerabilities described in the referenced Microsoft advisories are detailed in the "Associated Products" table in the "Product Sets" section.

Vulnerability Characteristics

MS10-050 Vulnerability in Windows Movie Maker Could Allow Remote Code Execution (981997) This vulnerability has been assigned CVE identifier CVE-2010-2564. This vulnerability can be exploited remotely without authentication and requires user interaction.

Successful exploitation of this vulnerability may allow arbitrary code execution. The attack vector for exploitation of this vulnerability is through HTTP packets, which typically use TCP port 80 but may also use TCP ports 3128, 8000, 8010, 8080, 8888, and 24326. Although the Cisco ASA 5500 Series Adaptive Security Appliance, the Firewall Services Module (FWSM) for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers, and the Cisco ACE Application Control Engine Appliance and Module provide protection for potential attempts to exploit these vulnerabilities (a topic that is included in this document), web-based attacks (these include but are not limited to cross-site scripting, phishing, and web-based e-mail threats), and e-mail attachments could also be used to exploit this vulnerability.

MS10-051 Vulnerability in Microsoft XML Core Services Could Allow Remote Code Execution (2079403) This vulnerability has been assigned CVE identifier CVE-2010-2561 . This vulnerability can be exploited remotely without authentication and requires user interaction.

Successful exploitation of this vulnerability may allow arbitrary code execution. The attack vector for exploitation of this vulnerability is through HTTP packets, which typically use TCP port 80 but may also use TCP ports 3128, 8000, 8010, 8080, 8888, and 24326. Although the Cisco ASA 5500 Series Adaptive Security Appliance, the Firewall Services Module (FWSM) for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers, and the Cisco ACE Application Control Engine Appliance and Module provide protection for potential attempts to exploit these vulnerabilities (a topic that is included in this document), web-based attacks (these include but are not limited to cross-site scripting, phishing, and web-based e-mail threats), and e-mail attachments could also be used to exploit this vulnerability.

MS10-054 Vulnerabilities in SMB Server Could Allow Remote Code Execution (982214): These vulnerabilities have been assigned the following CVE identifiers:

• CVE-2010-2550
• CVE-2010-2551
• CVE-2010-2552

These vulnerabilities can be exploited remotely without authentication and without user interaction. Successful exploitation of the vulnerability for CVE-2010-2550 may allow arbitrary code execution. Successful exploitation of the vulnerabilities for CVE-2010-2551 and CVE-2010-2552 may result in a denial of service (DoS) condition requiring a manual restart of the affected device. The attack vector for exploitation of these vulnerabilities is through Microsoft Server Message Block (SMB) using TCP port 139 and TCP port 445 packets.

MS10-055 Vulnerability in Cinepak Codec Could Allow Remote Code Execution (982665): This vulnerability has been assigned CVE identifier CVE-2010-2553. This vulnerability can be exploited remotely without authentication and requires user interaction.

Successful exploitation of this vulnerability may allow arbitrary code execution. The attack vector for exploitation of this vulnerability is through HTTP packets, which typically use TCP port 80 but may also use TCP ports 3128, 8000, 8010, 8080, 8888, and 24326. Although the Cisco ASA 5500 Series Adaptive Security Appliance, the Firewall Services Module (FWSM) for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers, and the Cisco ACE Application Control Engine Appliance and Module provide protection for potential attempts to exploit these vulnerabilities (a topic that is included in this document), web-based attacks (these include but are not limited to cross-site scripting, phishing, and web-based e-mail threats), and e-mail attachments could also be used to exploit this vulnerability.

MS10-060 Vulnerabilities in the Microsoft .NET Common Language Runtime and in Microsoft Silverlight Could Allow Remote Code Execution (2265906) These vulnerabilities have been assigned CVE identifiers CVE-2010-0019 and CVE-2010-1898. These vulnerabilities can be exploited remotely without authentication and require user interaction.

Successful exploitation of this vulnerability may allow arbitrary code execution. The attack vector for exploitation of this vulnerability is through HTTP packets, which typically use TCP port 80 but may also use TCP ports 3128, 8000, 8010, 8080, 8888, and 24326. Although the Cisco ASA 5500 Series Adaptive Security Appliance, the Firewall Services Module (FWSM) for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers, and the Cisco ACE Application Control Engine Appliance and Module provide protection for potential attempts to exploit these vulnerabilities (a topic that is included in this document), cross-site scripting and phishing could also be used to exploit these vulnerabilities.

For additional information about cross-site scripting attacks and the methods used to exploit these vulnerabilities, refer to the Cisco Applied Mitigation Bulletin Understanding Cross-Site Scripting (XSS) Threat Vectors.

Information about vulnerable, unaffected, and fixed software is available in the Microsoft Security Bulletin Summary for August, 2010, which is available at the following link: http://www.microsoft.com/technet/security/bulletin/MS10-aug.mspx

Mitigation Technique Overview

The vulnerabilities that have a client software attack vector, or can be exploited locally on the vulnerable device, or require user interaction or can be exploited using web-based attacks (these include but are not limited to cross-site scripting, phishing, and web-based e-mail threats), and e-mail attachments are in the following list:

• MS10-047
• MS10-048
• MS10-049
• MS10-050
• MS10-051
• MS10-052
• MS10-053
• MS10-055
• MS10-056
• MS10-057
• MS10-058
• MS10-059
• MS10-060

These vulnerabilities are best mitigated at the endpoint through software updates, user education, desktop administration best practices, and endpoint protection software such as Cisco Security Agent Host Intrusion Prevention System (HIPS) or antivirus products.

The vulnerabilities that have a network mitigation are in the following list. Cisco devices provide several countermeasures for these vulnerabilities. This section of the document provides an overview of these techniques.

• MS10-050
• MS10-051
• MS10-054
• MS10-055
• MS10-060

Cisco IOS Software can provide effective means of exploit prevention using transit access control lists (tACLs).

This protection mechanism filters and drops packets that are attempting to exploit the vulnerabilities that have a network attack vector.

Effective means of exploit prevention can also be provided by Cisco ASA 5500 Series Adaptive Security Appliance and the Firewall Services Module (FWSM) for Cisco Catalyst 6500

• tACLs
• Application layer protocol inspection

These protection mechanisms filter and drop packets that are attempting to exploit the vulnerabilities that have a network attack vector.

Effective exploit prevention can also be provided by the Cisco ACE Application Control Engine Appliance and Module using Application Protocol Inspection.

Effective use of Cisco Intrusion Prevention System (IPS) event actions provides visibility into and protection against attacks that attempt to exploit these vulnerabilities as discussed later in this document.

Cisco IOS NetFlow records can provide visibility into network-based exploitation attempts.

Cisco IOS Software, Cisco ASA, FWSM firewalls, and Cisco ACE Application Control Engine Appliance and Module can provide visibility through syslog messages and counter values displayed in the output from show commands.

The Cisco Security Monitoring, Analysis, and Response System (Cisco Security MARS) appliance can also provide visibility through incidents, queries, and event reporting.

Risk Management

Organizations are advised to follow their standard risk evaluation and mitigation processes to determine the potential impact of these vulnerabilities. Triage refers to sorting projects and prioritizing efforts that are most likely to be successful. Cisco has provided documents that can help organizations develop a risk-based triage capability for their information security teams. Risk Triage for Security Vulnerability Announcements and Risk Triage and Prototyping can help organizations develop repeatable security evaluation and response processes.

Device-Specific Mitigation and Identification

Caution: The effectiveness of any mitigation technique depends on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. As with any configuration change, evaluate the impact of this configuration prior to applying the change.

Specific information about mitigation and identification is available for these devices:

• Cisco IOS Routers and Switches
• Cisco IOS NetFlow
• Cisco ASA and FWSM Firewalls
• Cisco ACE
• Cisco Intrusion Prevention System
• Cisco Security Monitoring, Analysis, and Response System

Cisco IOS Routers and Switches

Mitigation: Transit Access Control Lists

For MS10-054, to protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy transit access control lists (tACLs) to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against these vulnerabilities that have a network attack vector when the attack comes from a trusted source address.

The tACL policy denies unauthorized SMB packets on TCP ports 139 and 445 that are sent to affected devices. In the following example, 192.168.60.0/24 is the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered a trusted source that requires access to the affected devices. Care should be taken to allow required traffic for routing and administrative access prior to denying all unauthorized traffic.

Additional information about tACLs is available in Transit Access Control Lists: Filtering at Your Edge.

!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable TCP ports for MS10-054
!
access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 139
access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 445
!
!-- The following vulnerability-specific access control entries
!-- (ACEs) can aid in identification of attacks against
!-- MS10-054
!
access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 139
access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 445

!
!-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance
!-- with existing security policies and configurations
!
!-- Explicit deny for all other IP traffic
!
access-list 150 deny ip any any
!
!-- Apply tACL to interfaces in the ingress direction
interface GigabitEthernet0/0
 ip access-group 150 in

Note that filtering with an interface access list will elicit the transmission of ICMP unreachable messages back to the source of the filtered traffic. Generating these messages could have the undesired effect of increasing CPU utilization on the device. In Cisco IOS Software, ICMP unreachable generation is limited by default to one packet every 500 milliseconds. ICMP unreachable message generation can be disabled using the interface configuration command no ip unreachables. ICMP unreachable rate limiting can be changed from the default using the global configuration command ip icmp rate-limit unreachable interval-in-ms.

Identification: Transit Access Control Lists

After the administrator applies the tACL to an interface, the show ip access-lists command will identify the number of SMB packets on TCP ports 139 and 445 that have been filtered. Administrators are advised to investigate filtered packets to determine if they are attempts to exploit these vulnerabilities. Example output for show ip access-lists 150 follows:

router#show ip access-lists 150
Extended IP access list 150
    10 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 139
    20 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 445
    30 deny tcp any 192.168.60.0 0.0.0.255 eq 139 (12 matches)
    40 deny tcp any 192.168.60.0 0.0.0.255 eq 445 (26 matches)
    50 deny ip any any

In the preceding example, access list 150 has dropped the following packets received from an untrusted host or network:

• 12 SMB packets on TCP port 139 for ACE line 30
• 26 SMB packets on TCP port 445 for ACE line 40

For additional information about investigating incidents using ACE counters and syslog events, reference the Identifying Incidents Using Firewall and IOS Router Syslog Events Applied Intelligence white paper.

Administrators can use Embedded Event Manager to provide instrumentation when specific conditions are met, such as ACE counter hits. The Applied Intelligence white paper Embedded Event Manager in a Security Context provides additional details about how to use this feature.

Identification: Access List Logging

The log and log-input access control list (ACL) option will cause packets that match specific ACEs to be logged. The log-input option enables logging of the ingress interface in addition to the packet source and destination IP addresses and ports.

Caution: ACL logging can be very CPU intensive and must be used with extreme caution. Factors that drive the CPU impact of ACL logging are log generation, log transmission, and process switching to forward packets that match log-enabled ACEs.

For Cisco IOS Software, the ip access-list logging interval interval-in-ms command can limit the effects of process switching induced by ACL logging. The logging rate-limit rate-per-second [except loglevel] command limits the impact of log generation and transmission.

The CPU impact from ACL logging can be addressed in hardware on the Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers with Supervisor Engine 720 or Supervisor Engine 32 using optimized ACL logging.

For additional information about the configuration and use of ACL logging, reference the Understanding Access Control List Logging Applied Intelligence white paper.

Cisco IOS NetFlow

Identification: Traffic Flow Identification Using NetFlow Records

For MS10-054, administrators can configure Cisco IOS NetFlow on Cisco IOS routers and switches to aid in the identification of traffic flows that may be attempts to exploit the vulnerabilities described in MS10-054. Administrators are advised to investigate flows to determine whether they are attempts to exploit the vulnerabilities or whether they are legitimate traffic flows.

router#show ip cache flow

IP packet size distribution (90784136 total packets):
   1-32   64   96  128  160  192  224  256  288  320  352  384  416  448  480
   .000 .698 .011 .001 .004 .005 .000 .004 .000 .000 .003 .000 .000 .000 .000

    512  544  576 1024 1536 2048 2560 3072 3584 4096 4608
   .000 .001 .256 .000 .010 .000 .000 .000 .000 .000 .000

IP Flow Switching Cache, 4456704 bytes
  1885 active, 63651 inactive, 59960004 added
  129803821 ager polls, 0 flow alloc failures
  Active flows timeout in 30 minutes
  Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 402056 bytes
  0 active, 16384 inactive, 0 added, 0 added to flow
  0 alloc failures, 0 force free
  1 chunk, 1 chunk added
  last clearing of statistics never
Protocol         Total    Flows   Packets Bytes  Packets Active(Sec) Idle(Sec)
--------         Flows     /Sec     /Flow  /Pkt     /Sec     /Flow     /Flow
TCP-Telnet    11393421      2.8         1    48      3.1       0.0       1.4
TCP-FTP            236      0.0        12    66      0.0       1.8       4.8
TCP-FTPD            21      0.0     13726  1294      0.0      18.4       4.1
TCP-WWW          22282      0.0        21  1020      0.1       4.1       7.3
TCP-X              719      0.0         1    40      0.0       0.0       1.3
TCP-BGP              1      0.0         1    40      0.0       0.0      15.0
TCP-Frag         70399      0.0         1   688      0.0       0.0      22.7
TCP-other     47861004     11.8         1   211     18.9       0.0       1.3
UDP-DNS            582      0.0         4    73      0.0       3.4      15.4
UDP-NTP         287252      0.0         1    76      0.0       0.0      15.5
UDP-other       310347      0.0         2   230      0.1       0.6      15.9
ICMP             11674      0.0         3    61      0.0      19.8      15.5
IPv6INIP            15      0.0         1  1132      0.0       0.0      15.4
GRE                  4      0.0         1    48      0.0       0.0      15.3 
Total:        59957957     14.8         1   196     22.5       0.0       1.5

SrcIf         SrcIPaddress    DstIf         DstIPaddress    Pr SrcP DstP  Pkts
Gi0/0         192.168.10.201  Gi0/1         192.168.60.102  06 0984 008B    17
Gi0/0         192.168.11.54   Gi0/1         192.168.60.158  06 0911 01BD    33
Gi0/1         192.168.150.60  Gi0/0         10.89.16.226    06 0016 12CA     1
Gi0/0         192.168.13.97   Gi0/1         192.168.60.28   06 0B3E 01BD    55
Gi0/0         192.168.10.17   Gi0/1         192.168.60.97   06 0B89 01BD    41
Gi0/0         10.88.226.1     Gi0/1         192.168.202.22  11 007B 007B     1
Gi0/0         192.168.12.185  Gi0/1         192.168.60.239  06 0BD7 008B    19

Gi0/0         10.89.16.226    Gi0/1         192.168.150.60  06 12CA 0016     1
router#

In the preceding example, there are multiple flows for SMB packets on TCP port 139 (hex value 008B) and TCP port 445 (hex value 01BD) .

This traffic is sent to addresses in the 192.168.60.0/24 address block, that is used by affected devices. The packets in these flows may indicate an attempt to exploit this vulnerability. Administrators are advised to compare these flows to baseline utilization for SMB traffic sent on TCP port 139 and TCP port 445 and also investigate the flows to determine whether they are sourced from untrusted hosts or networks.

To view only the traffic flows for SMB packets on TCP port 139 (hex value 008B) and TCP port 445 (hex value 01BD), the command show ip cache flow | include SrcIf|_06_.*(008B|01BD)_ will display the related TCP NetFlow records as shown here:

TCP Flows

router#show ip cache flow | include SrcIf|_06_.*(008B|01BD)_

SrcIf         SrcIPaddress     DstIf         DstIPaddress    Pr SrcP DstP  Pkts
Gi0/0         192.168.10.201   Gi0/1         192.168.60.102  06 0984 008B    17
Gi0/0         192.168.11.54    Gi0/1         192.168.60.158  06 0911 01BD    33
Gi0/0         192.168.13.97    Gi0/1         192.168.60.28   06 0B3E 01BD    55
Gi0/0         192.168.10.17    Gi0/1         192.168.60.97   06 0B89 01BD    41
Gi0/0         192.168.12.185   Gi0/1         192.168.60.239  06 0BD7 008B    19

router#

Cisco ASA and FWSM Firewalls

Mitigation: Transit Access Control Lists

For MS10-054, to protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy tACLs to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against these vulnerabilities when the attack originates from a trusted source address.

The tACL policy denies unauthorized SMB packets on TCP port 139 and TCP port 445 that are sent to affected devices. In the following example, 192.168.60.0/24 is the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered a trusted source that requires access to the affected devices. Care should be taken to allow required traffic for routing and administrative access prior to denying all unauthorized traffic.

Additional information about tACLs is in Transit Access Control Lists: Filtering at Your Edge.

!
!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable TCP ports for MS10-054
!
access-list tACL-Policy extended permit tcp host 192.168.100.1 
     192.168.60.0 255.255.255.0 eq 139
access-list tACL-Policy extended permit tcp host 192.168.100.1 
     192.168.60.0 255.255.255.0 eq 445

!
!-- The following vulnerability-specific access control entries
!-- (ACEs) can aid in identification of attacks
!
access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 139
access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 445
!
!-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance
!-- with existing security policies and configurations
!
!-- Explicit deny for all other IP traffic
!
access-list tACL-Policy extended deny ip any any
!
!-- Apply tACL to interface(s) in the ingress direction
!

access-group tACL-Policy in interface outside

Mitigation: Application Layer Protocol Inspection

Application layer protocol inspection is available beginning in Software Release 7.2(1) for the Cisco ASA 5500 Series Adaptive Security Appliance and in Software Release 4.0(1) for the Firewall Services Module. This advanced security feature performs deep packet inspection of traffic that transits the firewall. Administrators may construct an inspection policy for applications that require special handling through the configuration of inspect class maps and inspect policy maps, which are applied by means of a global or interface service policy.

Additional information about application layer protocol inspection is in the Configuring Application Layer Protocol Inspection section of the Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2.

Caution: Application layer protocol inspection will decrease firewall performance. Administrators are advised to test performance impact in a lab environment before this feature is deployed in production environments.

HTTP Application Inspection
For MS10-050, MS10-051, MS10-055, and MS10-060 by using the HTTP inspection engine on the Cisco ASA 5500 Series Adaptive Security Appliances and the Firewall Services Module, administrators can configure regular expressions (regexes) for pattern matching and construct inspect class maps and inspect policy maps. These methods can help protect against specific vulnerabilities, such as the one described in this document and other threats that may be associated with HTTP traffic. The following HTTP application inspection configuration uses the Cisco Modular Policy Framework (MPF) to create a policy for inspection of traffic on TCP ports 80, 3128, 8000, 8010, 8080, 8888, and 24326, which are the default ports for the Cisco IPS #WEBPORTS variable. The HTTP application inspection policy will drop connections where the HTTP response body contains any of the regexes that are configured to match the ActiveX control that is associated with these vulnerabilities.

Caution: The configured regexes can match text strings at any location in the body of an HTML response. Care should be taken to ensure that legitimate business applications that use matching text strings without calling the ActiveX control are not affected. Additional information about regex syntax is in Creating a Regular Expression.

!
!-- Configure regexes that are associated with these vulnerabilities:
!-- MS10-050 File Extension:      "MSWMM"
!-- MS10-051 ActiveX Class ID:    
!--             "F5078F35-C551-11D3-89B9-0000F81FE221" 
!-- MS10-051 ActiveX Program ID:  "MSXML2.XMLHTTP.3.0"
!-- MS10-055 MIME type:           "video/x-msvideo"

!-- MS10-055 Identifying Response packet content: "RIFF"
!-- MS10-060 application type:    "application/x-silverlight"
! 

regex MS10-050 "\x2e[Mm][Ss][Ww][Mm][Mm]"
regex MS10-051_ProgID "[Mm][Ss][Xx][Mm][Ll]2\.
                       [Xx][Mm][Ll][Hh][Tt][Tt][Pp]\.3\.0"
regex MS10-051_CLSID "[Ff]5078[Ff]35[-][Cc]551[-]11[Dd]3[-]89[Bb]9[-]
                      0000[Ff]81[Ff][Ee]221"

regex MS10-055_MIME "video\x2fx\x2dmsvideo"
regex MS10-055_RIFF "[Rr][Ii][Ff][Ff]"
regex MS10-060 "application\x2f[Xx]\x2d
                [Ss][Ii][Ll][Vv][Ee][Rr][Ll][Ii][Gg][Hh][Tt]"
! 
!-- Configure a regex class to match on the two regular  
!-- expressions for MS10-051 that are configured above
! 
class-map type regex match-any MS10-051_regex_class
 match regex MS10-051_ProgID
 match regex MS10-051_CLSID


!
!-- Configure an object group for the default ports that 
!-- are used by the Cisco IPS #WEBPORTS variable, which 
!-- are TCP ports 80 (www), 3128, 8000, 8010, 8080, 8888, 
!-- and 24326
!

object-group service WEBPORTS tcp
 port-object eq www 
 port-object eq 3128 
 port-object eq 8000 
 port-object eq 8010 
 port-object eq 8080 
 port-object eq 8888 
 port-object eq 24326 
!
!-- Configure an access list that uses the WEBPORTS object 
!-- group, which will be used to match TCP packets that 
!-- are destined to the #WEBPORTS variable that is used 
!-- by a Cisco IPS device
!

access-list Webports-ACL extended permit tcp any any object-group WEBPORTS 
!
!-- Configure a class that uses the above-configured
!-- access list to match TCP packets that are destined
!-- to the ports that are used by the Cisco IPS #WEBPORTS
!-- variable
!
class-map Webports-Class
 match access-list Webports-ACL
!
!-- Configure http inspection classes to group traffic matches
!-- needed to identify the specific vulnerabilities
! 
class-map type inspect http match-all MS10-050_class
 match request uri regex MS10-050
 match request method get
! 
class-map type inspect http match-all MS10-050_post_class
 match request uri regex MS10-050
 match request method post
! 

class-map type inspect http match-all MS10-051_class  
 match response body regex class MS10-051_regex_class
! 

class-map type inspect http match-all MS10-055_class  
 match response header content-type regex MS10-055_MIME  
 match response body regex MS10-055_RIFF
! 
class-map type inspect http match-all MS10-060_class 
 match response body regex MS10-060
! 
!-- Configure an HTTP application inspection policy that  
!-- identifies, drops, and logs connections that contain HTTP  
!-- protocol violations and looks for and drops connections   
!-- that contain the traffic matches used to identify the
!-- specific vulnerabilities
! 
policy-map type inspect http MS_Aug_2010_policy
 parameters
!
!-- "protocol-violation" below is not required to
!-- mitigate these vulnerabilities but is
!-- included to provide more robust protection against
!-- potential HTTP attacks. Care should be taken to ensure that
!-- legitimate applications that do not fully conform to
!-- HTTP protocol standards are not dropped by this inspection
!
  protocol-violation action drop-connection
 class MS10-050_class
  drop-connection log
 class MS10-060_class
  drop-connection log
 class MS10-051_class
  drop-connection log
 class MS10-055_class
  drop-connection log
 class MS10-050_post_class
  drop-connection log

!
!-- Add the above-configured "Webports-Class" that matches 
!-- TCP packets that are destined to the default ports  
!-- that are used by the Cisco IPS #WEBPORTS variable to  
!-- the default policy "global_policy" and use it to 
!-- inspect HTTP traffic that transits the firewall
! 

policy-map global_policy
 class Webports-Class
  inspect http MS_Aug_2010_policy   

!
!-- By default, the policy "global_policy" is applied 
!-- globally, which results in the inspection of 
!-- traffic that enters the firewall from all interfaces 
!
service-policy global_policy global

For additional information about the configuration and use of object groups, reference the Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2 for Configuring Object Groups.

Additional information about HTTP application inspection and the MPF is in the HTTP Inspection Overview section of the Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2.

Identification: Transit Access Control Lists

After the tACL has been applied to an interface, administrators can use the show access-list command to identify the number of SMB packets on TCP port 139 and TCP 445 that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit these vulnerabilities. Example output for show access-list tACL-Policy follows:

firewall#show access-list tACL-Policy
access-list tACL-Policy; 5 elements
access-list tACL-Policy line 1 extended permit tcp host 192.168.100.1 
            192.168.60.0 255.255.255.0 eq netbios-ssn (hitcnt=71)
access-list tACL-Policy line 2 extended permit tcp host 192.168.100.1 
            192.168.60.0 255.255.255.0 eq 445 (hitcnt=214)
access-list tACL-Policy line 3 extended deny tcp any 192.168.60.0 255.255.255.0 
            eq netbios-ssn (hitcnt=351) 
access-list tACL-Policy line 4 extended deny tcp any 192.168.60.0 255.255.255.0 
            eq 445 (hitcnt=289)
access-list tACL-Policy line 5 extended deny ip any any (hitcnt=42)

In the preceding example, access list tACL-Policy has dropped the following packets received from an untrusted host or network:

• 351 SMB packets on TCP port 139 for ACE sequence identifier 3
• 289 SMB packets on TCP port 445 for ACE sequence identifier 4

Identification: Firewall Access List Syslog Messages

Firewall syslog message 106023 will be generated for packets denied by an access control entry (ACE) that does not have the log keyword present. Additional information about this syslog message is in Cisco ASA 5500 Series System Log Message, 8.2 - 106023.

Information about configuring syslog for the Cisco ASA 5500 Series Adaptive Security Appliance is in Monitoring - Configuring Logging. Information about configuring syslog on the FWSM for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers is in Monitoring the Firewall Services Module.

In the following example, the show logging | grep regex command extracts syslog messages from the logging buffer on the firewall. These messages provide additional information about denied packets that could indicate potential attempts to exploit the vulnerabilities that are described in this document. It is possible to use different regular expressions with the grep keyword to search for specific data in the logged messages.

Additional information about regular expression syntax is in Creating a Regular Expression.

firewall#show logging | grep 106023
  Aug 10 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.18/2944 
         dst inside:192.168.60.191/139 by access-group "tACL-Policy"
  Aug 10 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.200/2945 
         dst inside:192.168.60.33/139 by access-group "tACL-Policy"
  Aug 10 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.99/2946 
         dst inside:192.168.60.240/445 by access-group "tACL-Policy"

  Aug 10 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.100/2947 
         dst inside:192.168.60.115/139 by access-group "tACL-Policy"
  Aug 10 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.88/2949 
         dst inside:192.168.60.38/445 by access-group "tACL-Policy"
  Aug 10 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.175/2950 
         dst inside:192.168.60.250/445 by access-group "tACL-Policy"
firewall#

In the preceding example, the messages logged for the tACL tACL-Policy show SMB packets for TCP port 139 and TCP port 445 sent to the address block assigned to the affected devices.

Additional information about syslog messages for ASA security appliances is in Cisco ASA 5500 Series System Log Messages, 8.2. Additional information about syslog messages for the FWSM is in Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Logging System Log Messages.

For additional information about investigating incidents using syslog events, reference the Identifying Incidents Using Firewall and IOS Router Syslog Events Applied Intelligence white paper.

Identification: Application Layer Protocol Inspection

Firewall syslog message 415006 will be generated when the Uniform Resource Identifier (URI) matches a user-defined regular expression. The syslog message will identify the corresponding HTTP class and HTTP policy and indicate the action applied to the HTTP connection. Additional information about this syslog message is in Cisco ASA 5500 Series System Log Message, 8.2 - 415006.

Firewall syslog message 415007 will be generated when an HTTP message body matches a user-defined regular expression. The syslog message will identify the corresponding HTTP class and HTTP policy and indicate the action applied to the HTTP connection. Additional information about this syslog message is in Cisco ASA 5500 Series System Log Message, 8.2 - 415007.

Information about configuring syslog for the Cisco ASA 5500 Series Adaptive Security Appliance is in Monitoring - Configuring Logging. Information about configuring syslog on the FWSM for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers is in Monitoring the Firewall Services Module.

In the following example, the show logging | grep regex command extracts syslog messages from the logging buffer on the firewall. These messages provide additional information about denied packets that could indicate attempts to exploit these vulnerabilities. Administrators can use different regular expressions with the grep keyword to search for specific data in the logged messages.

Additional information about regular expression syntax is in Creating a Regular Expression.

HTTP Application Inspection

firewall#show logging | grep 415006

  Aug 10 2010 14:36:20: %ASA-5-415006: HTTP - matched Class 23: 
         MS10-050_class in policy-map MS_Aug_2010_policy, URI matched - 
         Dropping connection from inside:192.168.60.88/2135 to 
         outside:192.0.2.63/80
  Aug 10 2010 14:37:02: %ASA-5-415006: HTTP - matched Class 26: 
         MS10-050_post_class in policy-map MS_Aug_2010_policy, URI matched - 
         Dropping connection from inside:192.168.60.71/1830 to 
         outside:192.0.2..63/80

firewall#show logging | grep 415007
  Aug 10 2010 14:35:54: %ASA-5-415007: HTTP - matched Class 22: 
         MS10-051_class in policy-map MS_Aug_2010_policy, Body matched - 
         Dropping connection from inside:192.168.60.85/2130 to 
         outside:192.0.2.63/80
  Aug 10 2010 14:35:55: %ASA-5-415007: HTTP - matched Class 20: 
         MS10-055_class in policy-map MS_Aug_2010_policy, Body matched - 
         Dropping connection from inside:192.168.60.86/2133 to 
         outside:192.0.2.63/80
  Aug 10 2010 14:36:03: %ASA-5-415007: HTTP - matched Class 24:
         MS10-060_class in policy-map MS_Aug_2010_policy, Body matched - 
         Dropping connection from inside:192.168.60.87/2129 to 
         outside:192.0.2.63/80

With HTTP application inspection enabled, the show service-policy inspect protocol command will identify the number of HTTP packets that are inspected and dropped by this feature. The following example shows output for show service-policy inspect http:

firewall# show service-policy inspect http

Global policy: 
  Service-policy: global_policy
    Class-map: inspection_default
    Class-map: Webports-Class
      Inspect: http MS_Aug_2010_policy, packet 25, drop 5, reset-drop 0

        protocol violations
          packet 0
        class MS10-050_class
          drop-connection log, packet 1
        class MS10-060_class
          drop-connection log, packet 1
        class MS10-051_class
          drop-connection log, packet 1
        class MS10-055_class
          drop-connection log, packet 1
        class MS10-050_post_class
          drop-connection log, packet 1

In the preceding example, 25 HTTP packets have been inspected and 5 HTTP packets have been dropped, one by each the applied class-maps.

Cisco ACE

Mitigation: Application Protocol Inspection

Application protocol inspection is available for the Cisco ACE Application Control Engine Appliance and Module. This advanced security feature performs deep packet inspection of traffic that transits the Cisco ACE. Administrators can construct an inspection policy for applications that require special handling through the configuration of inspect class maps and inspect policy maps, which are applied by me3ans of a global or interface service policy.

Additional information about application protocol inspection is in the Configuring Application Protocol Inspection section of the Cisco ACE 4700 Series Appliance Security Configuration Guide.

HTTP Deep Packet Inspection

To conduct HTTP deep packet inspection for MS10-050, MS10-051, MS10-055, and MS10-060, administrators can configure regular expressions (regexes) for pattern matching and construct inspect class maps and inspect policy maps. These methods can help protect against specific vulnerabilities, such as the one described in this document, and other threats that may be associated with HTTP traffic. The following HTTP application protocol inspection configuration inspects traffic on TCP ports 80, 3128, 8000, 8010, 8080, 8888, and 24326, which are the default ports for the Cisco IPS #WEBPORTS variable. The HTTP application protocol inspection policy will drop connections where the HTTP content contains any of the regexes that are configured to match the ActiveX control that is associated with these vulnerabilities.

Caution: The configured regexes can match text strings at any location in the content of an HTML packet. Care should be taken to ensure that legitimate business applications that use matching text strings without calling the ActiveX control are not affected.

 ! 
 !-- Configure HTTP application inspection classes that
 !-- looks for HTTP packets that contain the regexes 
 !-- that are associated with these vulnerabilities:
 !-- MS10-050 File Extension:      "MSWMM"
 !-- MS10-051 ActiveX Class ID:    
 !--             "F5078F35-C551-11D3-89B9-0000F81FE221" 
 !-- MS10-051 ActiveX Program ID:  "MSXML2.XMLHTTP.3.0"
 !-- MS10-055 File Extension:      "AVI"
 !-- MS10-060 application type:    "data:application/x-silverlight"

 ! 
   
 class-map type http inspect match-any ms10-050
   match url .*+\.[Mm][Ss][Ww][Mm][Mm]
 class-map type http inspect match-any ms10-051
   match content ".*[Ff]5078[Ff]35[-][Cc]551[-]11[Dd]3[-]
                  89[Bb]9[-]0000[Ff]81[Ff][Ee]221.*"
   match content ".*[Mm][Ss][Xx][Mm][Ll]2\.
                  [Xx][Mm][Ll][Hh][Tt][Tt][Pp]\.3\.0.*"
 class-map type http inspect match-all ms10-055
   match url .*+\x2e[Aa][Vv][Ii]
 class-map type http inspect match-any ms10-060
   match content ".*[Dd][Aa][Tt][Aa]\x3a[Aa][Pp][Pp][Ll][Ii][Cc]
                  [Aa][Tt][Ii][Oo][Nn]\x2f[Xx]\x2d[Ss][Ii][Ll][Vv]
                  [Ee][Rr][Ll][Ii][Gg][Hh][Tt].*"
 !
 !-- Configure an HTTP application inspection policy 
 !-- that identifies, resets and logs connections that
 !-- match the HTTP application inspection classes  
 !-- that are configured above
 !

 policy-map type inspect http all-match MS-Aug-2010_policy
  class ms10-050
    reset log
  class ms10-051
    reset log
  class ms10-055
    reset log
  class ms10-060
    reset log
 !
 !-- Configure an access list that matches TCP packets
 !-- that are destined to the #WEBPORTS variable that is
 !-- used by a Cisco IPS device
 !

 access-list WEBPORTS line 8 extended permit tcp any any eq www 
 access-list WEBPORTS line 16 extended permit tcp any any eq 3128 
 access-list WEBPORTS line 24 extended permit tcp any any eq 8000 
 access-list WEBPORTS line 32 extended permit tcp any any eq 8010 
 access-list WEBPORTS line 40 extended permit tcp any any eq 8080 
 access-list WEBPORTS line 48 extended permit tcp any any eq 8888 
 access-list WEBPORTS line 56 extended permit tcp any any eq 24326 
 !
 !-- Configure a Layer 4 class that uses the above-configured
 !-- access list to match TCP packets that are destined
 !-- to the ports that are used by the Cisco IPS #WEBPORTS
 !-- variable
 !

 class-map match-all L4-http-class
   match access-list WEBPORTS
 !
 !-- Configure a Layer 4 policy that applies the HTTP application
 !-- inspection policy configured above to TCP packets that
 !-- are destined to the ports that are used by the Cisco IPS
 !-- #WEBPORTS variable
 !
 policy-map multi-match L4-http-inspect-policy
   class L4-http-class
     inspect http policy MS-Aug-2010_policy
 !
 !-- Apply the configuration globally, which
 !-- results in the inspection of all traffic
 !-- that enters the ACE from all interfaces
 !

 service-policy input L4-http-inspect-policy
  

Identification: Application Protocol Inspection

HTTP Deep Packet Inspection

ACE syslog message 415006 will be generated when the Uniform Resource Identifier (URI) matches a user-defined regular expression. . The syslog message will identify the corresponding HTTP class and HTTP policy and indicate the action applied to the HTTP connection. Additional information about this syslog message is in Cisco ACE 4700 Series Appliance System Message Guide - System Message 415006.

ACE syslog message 415007 will be generated when an HTTP message body matches a user-defined regular expression. The syslog message will identify the corresponding HTTP class and HTTP policy and indicate the action applied to the HTTP connection. Additional information about this syslog message is in Cisco ACE 4700 Series Appliance System Message Guide - System Message 415007.

ACE/Admin# show logging | include 415006
Aug 10 2010 15:26:43: %ACE-5-415006: HTTP - matched ms10-055 in policy-map 
     L4-http-inspect-policy, URI matched - Resetting connection from 
     vlan130:192.0.2.71/1777 to vlan206:192.168.60.63/80 Connection 0x33
Aug 10 2010 15:30:33: %ACE-5-415006: HTTP - matched ms10-050 in policy-map
     L4-http-inspect-policy, URI matched - Resetting connection from 
     vlan130:192.0.2.71/1774 to vlan206:192.168.60.63/80 Connection 0x31

ACE/Admin# show logging | include 415007
Aug 10 2010 15:26:43: %ACE-5-415007: HTTP - matched ms10-051 in policy-map 
     L4-http-inspect-policy, Body matched - Resetting connection from 
     vlan206:192.168.60.63/80 to vlan130:192.0.2.94/1776 Connection 0x3a 
Aug 10 2010 15:30:33: %ACE-5-415007: HTTP - matched ms10-060 in policy-map 
     L4-http-inspect-policy, Body matched - Resetting connection from 
     vlan206:192.168.60.63/80 to vlan130:192.0.2.94/1778 Connection 0x3c 

When HTTP deep packet inspection is enabled, the show service-policy policyname detail command will identify the number of HTTP connections that are inspected and dropped by this feature. The following example shows output for show service-policy L4-http-inspect-policy detail:

ACE/Admin# show service-policy L4-http-inspect-policy detail

Status     : ACTIVE
Description: -----------------------------------------
Context Global Policy:
  service-policy: L4-http-inspect-policy
    class: L4-http-class
      inspect http:
        L7 inspect policy : MS-Aug-2010
        Url Logging: DISABLED
        curr conns       : 0         , hit count        : 5         
        dropped conns    : 0         
        client pkt count : 17        , client byte count: 3491                
        server pkt count : 16        , server byte count: 2482                
        conn-rate-limit      : 0         , drop-count : 0         
        bandwidth-rate-limit : 0         , drop-count : 0         
        L4 policy stats:
          Total Req/Resp: 8          , Total Allowed: 4         
          Total Dropped : 4          , Total Logged : 0         
        L7 Inspect policy : MS-Aug-2010
          class/match : ms10-050
            Inspect action :
               reset log
            Total Inspected      : 8          , Total Matched: 1         
            Total Dropped OnError: 0         
          class/match : ms10-051
            Inspect action :
               reset log
            Total Inspected      : 7          , Total Matched: 1         
            Total Dropped OnError: 0         
          class/match : ms10-055
            Inspect action :
               reset log
            Total Inspected      : 6          , Total Matched: 1         
            Total Dropped OnError: 0         
          class/match : ms10-060
            Inspect action :
               reset log
            Total Inspected      : 5          , Total Matched: 1         
            Total Dropped OnError: 0         

In the preceding example, eight total HTTP connections have been inspected and four HTTP connections have been dropped, one by each of the applied class-maps.

Additional information about HTTP Deep Packet Inspection and Application Protocol Inspection is in the Configuring Application Protocol Inspection section of the Cisco ACE 4700 Series Appliance Security Configuration Guide.

Cisco Intrusion Prevention System

Mitigation: Cisco IPS Signature Event Actions

Administrators can use the Cisco IPS appliances and services modules to provide threat detection and help prevent attempts to exploit several of the vulnerabilities described in this document. The following table provides an overview of CVE identifiers and the respective Cisco IPS signatures that will trigger events on potential attempts to exploit these vulnerabilities.

* Fidelity is also referred to as Signature Fidelity Rating (SFR) and is the relative measure of the accuracy of the signature (predefined). The value ranges from 0 through 100 and is set by Cisco Systems, Inc.

Administrators can configure Cisco IPS sensors to perform an event action when an attack is detected. The configured event action performs preventive or deterrent controls to help protect against an attack that is attempting to exploit the vulnerabilities listed in the preceding table.

Cisco IPS sensors are most effective when deployed in inline protection mode combined with the use of an event action. Automatic Threat Prevention for Cisco IPS 6.x sensors that are deployed in inline protection mode provides threat prevention against an attack that is attempting to exploit the vulnerability that is described in this document. Threat prevention is achieved through a default override that performs an event action for triggered signatures with a riskRatingValue greater than 90.

Cisco IPS 5.x sensors that are deployed in inline protection mode require an event action configured on a per-signature basis. Alternatively, administrators can configure an override that can perform an event action for any signatures that are triggered and are calculated as a high-risk threat. Using an event action on sensors deployed in inline protection mode provides the most effective exploit prevention.

For additional information about the risk rating and threat rating calculation, reference Risk Rating and Threat Rating: Simplify IPS Policy Management.

IPS Signature Event Data

The following data has been compiled through remote monitoring services provided by the Cisco Remote Management Services team from a sample group of Cisco IPS sensors running Cisco IPS Signature Update version S506 or greater. The purpose of this data is to provide visibility into attempts to exploit the vulnerabilities released as part of the Microsoft August Security Update released on August 10, 2010. This data was gathered from events triggered on August 19, 2010.

Cisco Security Monitoring, Analysis, and Response System

Identification: Cisco Security Monitoring, Analysis, and Response System Incidents

The Cisco Security Monitoring, Analysis, and Response System (Cisco Security MARS) appliance can create incidents on events for the following Microsoft Security Bulletins. After the S506 dynamic signature update has been downloaded, using the following keywords for each of the respective IPS signatures and a query type of All Matching Event Raw Messages on the Cisco Security MARS appliance will provide a report that lists the incidents created by these IPS signatures.

Beginning with the 4.3.1 and 5.3.1 releases of Cisco Security MARS appliances, support for the Cisco IPS dynamic signature updates feature has been added. This feature downloads new signatures from Cisco.com or from a local web server, correctly processes and categorizes received events that match those signatures, and includes them in inspection rules and reports. These updates provide event normalization and event group mapping, and also enable the MARS appliance to parse new signatures from the IPS devices.

Caution: If dynamic signature updates are not configured, events that match these new signatures appear as unknown event type in queries and reports. Because MARS will not include these events in inspection rules, incidents may not be created for potential threats or attacks that occur within the network.

By default, this feature is enabled but requires configuration. If it is not configured, the following Cisco Security MARS rule will be triggered:

System Rule: CS-MARS IPS Signature Update Failure

When this feature is enabled and configured, administrators can determine the current signature version downloaded by MARS by selecting Help ] About and reviewing the IPS Signature Version value.

Additional information about dynamic signature updates and instructions for configuring dynamic signature updates is available for the Cisco Security MARS 4.3.1 and 5.3.1 releases.

Additional Information

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

Cisco Security Procedures

Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.

Related Information

• Microsoft Security Bulletin Summary for August, 2010
• Cisco Applied Mitigation Bulletins
• Cisco Security Intelligence Operations
• Cisco Guide to Harden Cisco IOS Devices
• Understanding Cross-Site Scripting (XSS) Threat Vectors
• Cisco IOS NetFlow - Home Page on Cisco.com
• Cisco IOS NetFlow White Papers
• NetFlow Performance Analysis
• Cisco Network Foundation Protection White Papers
• Cisco Network Foundation Protection Presentations
• Cisco Firewall Products - Home Page on Cisco.com
• Cisco ACE Application Control Engine Module Documentation
• Cisco 6.x Intrusion Prevention System
• Cisco IPS 6.x Signature Downloads
• Cisco IPS Signature Search Page
• Cisco Security Monitoring, Analysis, and Response System
• Common Vulnerabilities and Exposures (CVE)

Version 2, August 13, 2010, 12:51 PM: IPS signature event data from Cisco Remote Management Services is available for IPS signatures from August 12, 2010.

Version 1, August 10, 2010, 3:14 PM: This initial version of the Cisco Applied Mitigation Bulletin addresses the Microsoft Security Bulletin Release for August 2010.