Cisco Applied Mitigation Bulletin

Identifying and Mitigating Exploitation of the Cisco IOS Software Smart Install Denial of Service Vulnerability

Advisory ID: cisco-amb-20120328-smartinstall

http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20120328-smartinstall

Revision 1.0

For Public Release 2012 March 28 16:00  UTC (GMT)


Contents

Cisco Response
Device-Specific Mitigation and Identification
Additional Information
Revision History
Cisco Security Procedures
Related Information

Cisco Response

This Applied Mitigation Bulletin is a companion document to the PSIRT Security Advisory Cisco IOS Software Smart Install Denial of Service Vulnerability and provides identification and mitigation techniques that administrators can deploy on Cisco network devices.

This document provides identification and mitigation techniques that administrators can deploy on Cisco network devices.

Vulnerability Characteristics

The Smart Install feature in Cisco Catalyst Switches that are running Cisco IOS Software contains a vulnerability when it processes a malformed Smart Install over IP version 4 (IPv4) packets. This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability could cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition. The attack vector for exploitation is through Smart Install over IP version 4 (IPv4) packets using TCP port 4786.

This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2012-0385

Vulnerability Overview

Information about vulnerable, unaffected, and fixed software is available in the Cisco Security Advisory, which is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-smartinstall.

Mitigation Technique Overview

Cisco devices provide several countermeasures for these vulnerabilities. Administrators are advised to consider these protection methods to be general security best practices for infrastructure devices and the traffic that transits the network. This section of the document provides an overview of these techniques.

Cisco IOS Software can provide effective means of exploit prevention using Infrastructure access control lists (iACLs). Catalyst 6500 series switches can also provide effective means of exploit prevention using VLAN access control lists (VACLs). This protection mechanism filters and drops packets that are attempting to exploit this vulnerability.

Catalyst 6500 series switches can also provide effective means of exploit prevention using VLAN access control lists (VACLs). This protection mechanism filters and drops packets that are attempting to exploit this vulnerability.

Effective exploit prevention can also be provided by the Cisco ASA 5500 Series Adaptive Security Appliance, Cisco Catalyst 6500 Series ASA Services Module (ASASM), and the Firewall Services Module (FWSM) for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers using transit Access Control Lists (tACLs). This protection mechanism filters and drops packets that are attempting to exploit this vulnerability.

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

Cisco IOS Software, Cisco ASA, Cisco ASASM, Cisco 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.

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

The Cisco Security Manager 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 this vulnerability. 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

Mitigation: Infrastructure Access Control Lists

To protect infrastructure devices and minimize the risk, impact, and effectiveness of direct infrastructure attacks, administrators are advised to deploy infrastructure access control lists (iACLs) to perform policy enforcement of traffic sent to infrastructure equipment. Administrators can construct an iACL by explicitly permitting only authorized traffic sent to infrastructure devices in accordance with existing security policies and configurations. For the maximum protection of infrastructure devices, deployed iACLs should be applied in the ingress direction on all interfaces to which an IP address has been configured. An iACL workaround cannot provide complete protection against these vulnerabilities when the attack originates from a trusted source address.

The iACL policy denies unauthorized Smart Install over IPv4 packets on TCP port 4786 that are sent to affected devices. In the following example, 192.168.60.0/24 represent the IP address space that is used by the affected devices, and the hosts at 192.168.100.1 are considered trusted sources that require access to the affected devices. Care should be taken to allow required traffic for routing and administrative access prior to denying all unauthorized traffic. Whenever possible, infrastructure address space should be distinct from the address space used for user and services segments. Using this addressing methodology will assist with the construction and deployment of iACLs.

Additional information about iACLs is in Protecting Your Core: Infrastructure Protection Access Control Lists.

ip access-list extended Infrastructure-ACL-Policy
  !
  !-- Include explicit permit statements for trusted sources
  !-- that require access on the vulnerable protocols and ports
  !
  permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 4786
  !
  !-- The following vulnerability-specific access control entries
  !-- (ACE) can aid in identification of attacks
  !
  deny tcp any 192.168.60.0 0.0.0.255 eq 4786
  !
  !-- Explicit deny ACE for traffic sent to addresses configured within
  !-- the infrastructure address space
  !
  deny ip any 192.168.60.0 0.0.0.255  
  !
  !-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance
  !-- with existing security policies and configurations
  !
interface GigabitEthernet0/0
 ip access-group Infrastructure-ACL-Policy 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 to one packet every 500 milliseconds by default. 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: Infrastructure Access Control Lists

After the administrator applies the iACL to an interface, the show ip access-lists and show ipv6 access-list commands will identify the number of Smart Install over IPv4 packets on TCP port 4786 that have been filtered on interfaces on which the iACL is applied. Administrators should investigate filtered packets to determine whether they are attempts to exploit these vulnerabilities. Example output for show ip access-lists Infrastructure-ACL-Policy follows:

router#show ip access-lists Infrastructure-ACL-Policy
Extended IP access list Infrastructure-ACL-Policy
    10 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 4786 (188 matches)
    20 deny tcp any 192.168.60.0 0.0.0.255 eq 4786 (9 matches)
    30 deny ip any 192.168.60.0 0.0.0.255 (17 matches)
router#

In the preceding example, access list Infrastructure-ACL-Policy has dropped 9 Smart Install packets on TCP port 4786 for access control list entry (ACE) line 10.

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

Administrators can use Embedded Event Manager to provide instrumentation when specific conditions are met, such as ACE counter hits. The Cisco Security Intelligence Operations 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: Access control list 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 IPv4 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 Cisco Security Intelligence Operations white paper.

Mitigation: VLAN Access Control Lists

To protect the network from all packets that are bridged in a VLAN or that are routed into or out of a VLAN, administrators are advised to deploy VLAN access control lists (VACLs) to perform policy enforcement. Administrators can construct a VACL by explicitly permitting only authorized traffic to be bridged in a VLAN or routed into or out of a VLAN in accordance with existing security policies and configurations. A VACL workaround cannot provide complete protection against the vulnerabilities that have an IPv4 network attack vector when the attack comes from a trusted source address.

Note: VACLs differ from traditional Cisco IOS ACLs in that they apply to all packets as opposed to routed packets only. In addition to unicast traffic, VACLs also apply to multicast and broadcast traffic, so these types of packets must be accounted for in the VACL configuration.

The VACL policy denies unauthorized Smart Install packets on TCP port 4786 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 in VLAN 60, 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 VACLs is available in Catalyst 6500 Release 12.2SXH and Later Software Configuration Guide - Configuring Port ACLs and VLAN ACLs.

!
!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable port
!
ip access-list extended VACL-permit
  permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 4786
!
!-- The following vulnerability-specific access control entries
!-- (ACE) can aid in identification of attacks 
!
ip access-list extended VACL-deny
  permit tcp any 192.168.60.0 0.0.0.255 eq 4786
!
!-- Create an access list policy that will be applied 
!-- for VLAN access-map that permits all
!-- other Layer 2 & Layer 3 traffic
!--
!-- Explicit permit for all other IP traffic
!--
!-- Broadcast and multicast traffic must be accounted 
!-- for as well
!
ip access-list extended Permit-All
  permit ip any any
!
!-- Define the VLAN access map that will be used to
!-- perform policy enforcement (either permit or deny)
!-- on the traffic matched by the previously defined
!-- access control lists
!
vlan access-map VACL 10
match ip address VACL-permit
action forward
!
vlan access-map VACL 20
match ip address VACL-deny
action drop
!
vlan access-map VACL 30
match ip address Permit-All
action forward
!
!-- Apply the VACL policy to the VLAN or list of VLANs
!-- to filter traffic (Note:  The 'vlan-list' operator
!-- is a single VLAN or comma separated list of VLANs)
!
vlan filter VACL vlan-list 60
!

Note: In the preceding VACL example, the access control list entries (ACE) which match the potential exploit packets with the permit statement result in these packets to be discarded by the VLAN access-map drop statement.

Identification: VLAN Access Control Lists

After the administrator applies the VACL to a VLAN or list of VLANs, the show tcam interface vlan vlan-interface-number acl in ip command will identify the number of packets that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit this vulnerability. Example output for show tcam interface vlan 60 acl in ip follows:

Note: An administrator can see additional access control entry statistics using the show tcam interface vlan vlan-interface-number acl in ip detail command.

switch#show tcam interface vlan 60 acl in ip

* Global Defaults shared

Entries from Bank 0

Entries from Bank 1

    permit       tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 4786 (13 matches)
    deny         tcp any 192.168.60.0 0.0.0.255 eq 4786 (35 matches)
    permit       ip any any (379 matches)
switch#

In the preceding example, rules for VACL policy VACL have dropped 35 Smart Install packets on TCP port 4786.

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.

Cisco IOS NetFlow and Cisco IOS Flexible NetFlow

Identification: IPv4 Traffic Flow Identification Using Cisco IOS NetFlow

Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and switches to aid in the identification of IPv4 traffic flows that may be attempts to exploit these vulnerabilities. Administrators are advised to investigate flows to determine whether they are attempts to exploit these 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 12B2     1
Gi0/0         192.168.11.54   Gi0/1         192.168.60.158  06 0911 12B2     3
Gi0/1         192.168.150.60  Gi0/0         10.89.16.226    06 0016 12CA     1
Gi0/0         10.88.226.1     Gi0/1         192.168.202.22  11 007B 007B     1
router#

In the preceding example, there are multiple flows for SmartInstall on TCP port 4786 (hex value 12B2).

As shown in the following example, to view only the Smart Install packets on TCP port 4786 (hex value 12B2), use the show ip cache flow | include SrcIf|_06_.*12B2 command to display the related Cisco NetFlow records:

TCP Flows
router#show ip cache flow | include SrcIf|_06_.*00A1
SrcIf         SrcIPaddress     DstIf         DstIPaddress    Pr SrcP DstP  Pkts
Gi0/0         192.168.10.201  Gi0/1         192.168.60.102  06 0984 12B2     1
Gi0/0         192.168.11.54   Gi0/1         192.168.60.158  06 0911 12B2     3
router#

Identification: IPv4 Traffic Flow Identification Using Cisco Flexible NetFlow

Introduced in Cisco IOS Software Releases 12.2(31)SB2 and 12.4(9)T, Cisco IOS Flexible NetFlow improves original Cisco NetFlow by adding the capability to customize the traffic analysis parameters for the administrator's specific requirements. Original Cisco NetFlow uses a fixed seven tuples of IP information to identify a flow, whereas Cisco IOS Flexible NetFlow allows the flow to be user defined. It facilitates the creation of more complex configurations for traffic analysis and data export by using reusable configuration components.

The following example output is from a Cisco IOS device that is running a version of Cisco IOS Software in the 15.1T train. Although the syntax will be almost identical for the 12.4T and 15.0 trains, it may vary slightly depending on the actual Cisco IOS release being used. In the following configuration, Cisco IOS Flexible NetFlow will collect information on interface GigabitEthernet0/0 for incoming IPv4 flows based on source IPv4 address, as defined by the match ipv4 source address key field statement. Cisco IOS Flexible NetFlow will also include nonkey field information about source and destination IPv4 addresses, protocol, ports (if present), ingress and egress interfaces, and packets per flow.

!
!-- Configure key and nonkey fields
!-- in the user-defined flow record
!
flow record FLOW-RECORD-ipv4
 match ipv4 source address
 collect ipv4 protocol
 collect ipv4 destination address
 collect transport source-port
 collect transport destination-port
 collect interface input
 collect interface output
 collect counter packets
!
!-- Configure the flow monitor to
!-- reference the user-defined flow 
!-- record
!
flow monitor FLOW-MONITOR-ipv4
 record FLOW-RECORD-ipv4
!
!-- Apply the flow monitor to the interface
!-- in the ingress direction
!
interface GigabitEthernet0/0
 ip flow monitor FLOW-MONITOR-ipv4 input

The Cisco IOS Flexible NetFlow flow output is as follows:

router#show flow monitor FLOW-MONITOR-ipv4 cache format table
  Cache type:                               Normal
  Cache size:                                 4096
  Current entries:                               6
  High Watermark:                                1

  Flows added:                                   9181
  Flows aged:                                    9175
    - Active timeout      (  1800 secs)          9000
    - Inactive timeout    (    15 secs)           175
    - Event aged                                    0
    - Watermark aged                                0
    - Emergency aged                                0

IPV4 SRC ADDR    ipv4 dst addr    trns src port  trns dst port  intf input     intf output     pkts     ip prot
===============  ===============  =============  =============  =============  ==============  =======  =======
 192.168.10.201   192.168.60.102           1456           4786          Gi0/0           Gi0/1     1128       6
 192.168.11.54    192.168.60.158            123           4786          Gi0/0           Gi0/1     2212       6
 192.168.150.60     10.89.16.226           2567            443          Gi0/0           Gi0/1       13       6

To view only the Smart Install on TCP port 4786, use the show flow monitor FLOW-MONITOR-ipv4 cache format table | include IPV4 DST ADDR |_4786_.*_6 command to display the related NetFlow records.

For more information about Cisco IOS Flexible NetFlow, refer to Flexible Netflow Configuration Guide, Cisco IOS Release 15.1M&T and Cisco IOS Flexible NetFlow Configuration Guide, Release 12.4T.

Cisco ASA, Cisco ASASM, and Cisco FWSM Firewalls

Mitigation: Transit Access Control Lists

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 Smart Install over IPv4 packets on TCP port 4786 that are sent to affected devices. In the following example, 192.168.60.0/24 and 2001:DB8:1:60::/64 represent the IP address space that is used by the affected devices, and the hosts at 192.168.100.1 and 2001:DB8::100:1 are considered trusted sources that require 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 protocols and ports
!
access-list tACL-Policy extended permit tcp host 192.168.100.1 
     192.168.60.0 255.255.255.0 eq 4786
!
!-- The following vulnerability-specific access control entries
!-- (ACE) can aid in identification of attacks
!
access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 4786
!
!-- 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 tACLs to interfaces in the ingress direction
!
access-group tACL-Policy in interface outside

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 Smart Install IPv4 packets on TCP port 4786 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; 3 elements; name hash: 0x3452703d
access-list tACL-Policy line 1 extended permit tcp host 192.168.100.1 
     192.168.60.0 255.255.255.0 eq 4786 (hitcnt=31)
access-list tACL-Policy line 2 extended deny tcp any 192.168.60.0 
     255.255.255.0 eq 4786 (hitcnt=8)
access-list tACL-Policy line 3 extended deny ip any any (hitcnt=8)

In the preceding example, access list tACL-Policy has dropped 8 Smart Install packets on TCP port 4786 received from an untrusted host or network. In addition, syslog message 106023 can provide valuable information, which includes the source and destination IP address, the source and destination port numbers, and the IP protocol for the denied packet.

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 Cisco Catalyst 6500 Series ASA Services Module is in 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
  Mar 28 2011 17:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.18/2944 
         dst inside:192.168.60.191/4786 by access-group "tACL-Policy"
  Mar 28 2011 17:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.200/2945 
         dst inside:192.168.60.33/4786 by access-group "tACL-Policy"
firewall#

In the preceding example, the messages logged for the tACL tACL-Policy show Smart Install packets for TCP port 4786 sent to the address block assigned to affected devices.

Additional information about syslog messages for Cisco ASA Series Adaptive Security Appliances is in Cisco ASA 5500 Series System Log Messages, 8.2. Additional information about syslog messages for Cisco Catalyst 6500 Series ASA Services Module is in the Analyzing Syslog Messages section of theCisco ASASM CLI Configuration Guide. Additional information about syslog messages for the Cisco 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 Cisco Security Intelligence Operations white paper.

Cisco Intrusion Prevention System

Mitigation: Cisco IPS Signature Table

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.

CVE ID Signature Release Signature ID Signature Name Enabled Severity Fidelity*
CVE-2012-0385 S636
1027/0 Cisco IOS Software Smart Install Denial of Service Vulnerability Yes Medium 80

* 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 7.x and 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.

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

Cisco Security Manager

Identification: Cisco Security Manager

Cisco Security Manager, Event Viewer

Beginning in software version 4.0, Cisco Security Manager can collect syslogs from Cisco firewalls and Cisco IPS devices and provides the Event Viewer, which can query for events that are related to the vulnerabilities that are described in this document.

Using the IPS Alert Events predefined view in the Event Viewer, the user can enter the search string 1027/0 in the event filter to return all captured events related to Cisco IPS signature 1027/0.

Using the following filters in the Firewall Denied Events predefined view in the Event Viewer provides all captured Cisco firewall access list deny syslog messages that could indicate potential attempts to exploit the vulnerabilities that are described in this document.

  • Use the Destination event filter to filter network objects that contain the IP address space that is used by the affected devices (for example, IPv4 address range 192.168.60.0/24
  • Use the Destination Service event filter to filter objects that contain TCP port 4786

An Event Type ID filter can be used with the Firewall Denied Events predefined view in the Event Viewer to filter the syslog IDs shown in the following list to provide all captured Cisco firewall deny syslog messages that could indicate potential attempts to exploit the vulnerabilities that are described in this document:

  • ASA-4-106023 (ACL deny)

For more information about Cisco Security Manager Events, refer to the Filtering and Querying Events section of the Cisco Security Manager User Guide.

Cisco Security Manager Report Manager

Beginning in software version 4.1, Cisco Security Manager supports the Report Manager, the Cisco IPS event reporting feature. This feature allows an administrator to define reports based on Cisco IPS events of interest. Reports can be scheduled or users can run ad hoc reports as required.

Using the Report Manager, the user can define an IPS Top Signatures report for Cisco IPS devices of interest based on time-range and signature characteristics. When the Signature ID is set to 1027/0, Cisco Security Manager will generate a comprehensive report that ranks the count of the alerts fired for the signature of interest compared to the total sum of all signature alerts shown in the report.

Also in the Report Manager, the Top Services report can be used with the following configuration to generate a report of events that indicate potential attempts to exploit the vulnerabilities that are described in this document:

  • Use the Destination IP network filter to filter network objects that contain the IP address space that is used by the affected devices (for example, IPv4 address range 192.168.60.0/24
  • Set an action of Deny on the Criteria settings page

For more information about Cisco Security Manager IPS Event Reporting refer to the Understanding IPS Top Reports section of the Cisco Security Manager User Guide.

Identification: Event Management System Partner Events

Cisco works with industry-leading Security Information and Event Management (SIEM) companies through the Cisco Developer Network. This partnership helps Cisco deliver validated and pretested SIEM systems that address business concerns such as long-term log archiving and forensics, heterogeneous event correlation, and advanced compliance reporting. Security Information and Event Management partner products can be leveraged to collect events from Cisco devices and then query the collected events for the incidents created by a Cisco IPS signature or deny syslog messages from firewalls that could indicate potential attempts to exploit the vulnerabilities that are described in this document. The queries can be made by Sig ID and Syslog ID as shown in the following list:

  • 1027/0 (Cisco IOS Software Smart Install Denial of Service Vulnerability)
  • ASA-4-106023 (ACL deny)

For more information about SIEM partners, refer to the Security Management System website.

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.

Revision History

Revision 1.0 2012-March-28 Initial public release

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/web/about/security/psirt/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


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