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Cisco Security Agent

Cisco Security Agent and Microsoft DNS 0Day Exploit

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PB405353

Summary

A vulnerability has been discovered in the Domain Name System (DNS) Server Service in Microsoft Windows 2000 and 2003 operating systems. The Microsoft DNS service Remote Procedure Call (RPC) implementation contains a stack buffer overflow. This vulnerability may allow a remote attacker to execute arbitrary code with SYSTEM privileges.
This vulnerability has already been exploited in several attacks. Cisco ® has obtained exploit files, and has confirmed that the Cisco Security Agent is effective in stopping these exploits, using the default security policy configuration. Current supported versions of Cisco Security Agent 4.5.x, 5.0.x, 5.1.x, and 5.2.x are all effective in stopping the exploits seen to date.

Details of the Vulnerability

Details of the vulnerability are documented by Microsoft 1 and by the Computer Emergency Response Team (CERT) 2:
A stack-based buffer overflow vulnerability in the RPC interface in the Domain Name System (DNS) Server Service in Microsoft Windows 2000 and 2003 operating systems allows remote attackers to execute arbitrary code, by sending a specially crafted RPC packet to the RPC management interface of an affected system.
RPC is a protocol that a program can use to request a service from a program located on another computer in a network. RPC helps with interoperability because the program using RPC does not have to understand the network protocols that are supporting communication. In RPC, the requesting program is the client and the service-providing program is the server.

How Cisco Security Agent Stops the Exploit

Cisco Security Agent default policies contain multiple rules that stop the exploit from doing any damage. No changes to the Cisco Security Agent binaries or default configuration are required to get this protection.
The following actions have been observed being blocked by Cisco Security Agent running the default security policies:

• The receipt of a TCP connection from a remote IP address

• Execution of a system function from a buffer, through a buffer overflow

• The attacked service attempted to execute a command shell (CMD.EXE)

This testing is shown in Figure 1.

Figure 1. Cisco Security Agent Default Configuration Stops the MS DNS 0-Day Exploit (Tested on Cisco Security Agent 5.2)

Note: The exploit was tested at Cisco, with the agent in Test mode, which will cause the agent to alert (but not block) malicious behavior. This was done to observe all possible ways that the Cisco Security Agent default policies would stop the exploit. When the agent is in Protect mode (the typical operational configuration), the first rule would kill the exploit: no subsequent events would be seen, since the exploit would be terminated before it could perform any malicious actions.

Testing was performed against the Cisco Security Agent default policies. No binary or policy update was needed for Cisco Security Agents to be effective. In short, this was a true test of "day-zero" protection. This is similar to what Cisco has seen with earlier exploits and worms-the default Cisco Security Agent configuration stopped the exploit, with no binary or policy updates required. The following is a partial list of prior worms and exploits that Cisco Security Agent has stopped via the default security policy settings:

Exploits

Worms

Exploits

Worms

ANI 0Day

OS vulnerability

MS06-035

OS vulnerability

Bagle

E-mail worm

MS06-040

OS vulnerability

BigYellow

Network worm

MS06-070

OS vulnerability

Blackworm

Network worm

MS07-014

Application vulnerabilities

Blaster

Network worm

Excel hlink dll

Application vulnerability

Bugbear

E-mail worm

MS RDS ActiveX

OS vulnerability

Code Red

Network worm

MS XML Core Svs

OS vulnerability

Debploit

Network worm

Nimda

Network worm

Fizzer

E-mail worm

Pentagone/Gonner

E-mail worm

Gator/Gain

Spyware

Sasser

Network worm

Hotbar

Spyware

Sircam

E-mail worm

HTTP Dir Traversal

Web server vulnerability

Sobig

E-mail worm

IE Text Range

Application vulnerability

Storm Trojan

E-mail worm

IE VML BO

Application vulnerability

WMF 0day

OS vulnerability

SQL Slammer

Network worm

Word BO

Application vulnerability

SQL Snake

Network worm

W32.Rinbot.H

Network worm

JPEG/GDI+

Malware downloader

Zotob

Network worm

MyDoom

E-mail worm

   

This exploit is only the latest example of new and mutating attacks that can seriously affect an organization's computing and network environments. The key to stopping these new attacks is two-fold: the ability to stop the attack without requiring any changes to the default configuration, and multiple rules in the default policies that provide defense in depth.