It has been over 2 years since I last wrote about malware exploitation of a major vulnerability in the Windows Server Service (MS06-040) by malware.

In 2006, worm authors were quick to adopt the remotely executed exploit in just 4 day following a security update released as part of the regular Patch Tuesdays - IRC-Mocbot, W32/Sdbot, W32/Spybot, W32/Opanki, et ceteras.

Now in 2008, we are faced with malware authors, motivated by profits, more organized, and are more likely to target zero-day vulnerabilities, as we have reported on several critical incidents we have discovered since 2006. Like déjà vu, Microsoft released an out-of-cycle security update today to address in-the-wild attacks against a new MS08-067 vulnerability targeting the same Windows Server Service.

Attacks seen in the wild so far seem to have come from variants of the Spy-Agent.da trojan. When run, it may not be immediately apparent to the victim that it was using any exploits. Taking a quick glimpse into the binary code of basesvc.dll (Spy-Agent.da.dll), one of the DLL components installed by Spy-Agent.da, one can see strings that would look very familiar to those familiar with MS06-040.

MS08-067 strings

On closer analysis, Spy-Agent.da.dll seeks out potentially vulnerable Windows machines in the local network, and sends maliciously crafted DCERPC requests to exploit the Server Service (SvrSvc).

MS08-067 exploit

When successful, hardcoded shellcode embedded within the malware, is executed on the targeted machines to download Spy-Agent.da (or possibly other variants or files) from a web server hosted in Japan.

MS08-067 shellcode
(shellcode after decoding)

Just hours following the patch release, public source code has already been seen distributing on the Internet. What more can I say ? Patch your systems ! Yes, NOW !

Spy-Agent.da and Spy-Agent.da.dll are now detected using the current 5414 DATs. See Dave’s blog for McAfee’s coverage.

(thanks to Joey Koo and Xiaobo Chen for providing analysis data and packet dumps used in this blog)