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SANS – Internet Storm Center – Windows WMF 0-day exploit in the wild

So far,Symantec, McAfee and F-Secure has heuristic detections for this 0–day exploit. Secunia has a write up on this exploit as well.

SANS – Internet Storm Center – Cooperative Cyber Threat Monitor And Alert System.

Handler’s Diary December 28th 2005

Windows WMF 0-day exploit in the wild (NEW)

Published: 2005-12-28,
Last Updated: 2005-12-28 10:04:51 UTC by Daniel Wesemann (Version: 1)

Just when we thought that this will be another slow day, a link to a working unpatched exploit in, what looks like Windows Graphics Rendering Engine, has been posted to Bugtraq.

The posted URL is   [ uni on seek. com/   d/t    1/  wmf_exp.  htm ]
(DON’T GO HERE UNLESS YOU KNOW WHAT YOU’RE DOING. Added spaces to avoid accidental clicking. See Firefox note below!!)

The HTML file runs another WMF (Windows Meta File) which executes a trojan dropper on a fully patched Windows XP SP2 machine. The dropper will then download Winhound, a fake anti-spyware/virus program which asks user to purchase a registered version of software in order to remove the reported threats.

During the test Johannes ran, it was interesting that the DEP (Data Execution Prevention) on his system stopped this from working. However, as this was tested on a AMD64 machine, we still have to confirm whether (or not) the software DEP also stops this – let us know if you tested this.

Internet Explorer will automatically launch the “Windows Picture and Fax Viewer”.  Note that Firefox users are not totally imune either. In my install of Firefox, a dialog box will ask me if I would like to load the image in “Windows Picture and Fax Viewer”. If I allow this to happen (“pictures are safe after all” NOT!), the exploit will execute.

For more information, see also http://vil.mcafeesecurity.com/vil/content/v_137760.htm and http://www.securityfocus.com/bid/16074/info

 
F-Secure Blog entry:
 
New WMF 0-day exploit Posted by Mika @ 08:38 GMT


There’s a new zero-day vulnerability related to Windows’ image rendering – namely WMF files (Windows Metafiles). Trojan downloaders, available from unionseek[DOT]com, have been actively exploiting this vulnerability. Right now, fully patched Windows XP SP2 machines machines are vulnerable, with no known patch.

spyware_traffic.png

The exploit is currently being used to distribute the following threats:
  Trojan-Downloader.Win32.Agent.abs
  Trojan-Dropper.Win32.Small.zp
  Trojan.Win32.Small.ga
  Trojan.Win32.Small.ev.

Some of these install hoax anti-malware programs the likes of Avgold.

spyware_warning.png

Note that you can get infected if you visit a web site that has an image file containing the exploit. Internet Explorer users might automatically get infected. Firefox users can get infected if they decide to run or download the image file.

In our tests (under XP SP2) older versions of Firefox (1.0.4) defaulted to open WMF files with “Windows Picture and Fax Viewer”, which is vulnerable. Newer versions (1.5) defaulted to open them with Windows Media Player, which is not vulnerable…but then again, Windows Media Player is not able to show WMF files at all so this might be a bug in Firefox. Opera 8.51 defaults to open WMF files with “Windows Picture and Fax Viewer” too. However, all versions of Firefox and Opera prompt the user first.

As a precaution, we recommend administrators to block access to unionseek[DOT]com and to filter all WMF files at HTTP proxy and SMTP level.

F-Secure Anti-Virus detects the offending WMF file as W32/PFV-Exploit with the 2005-12-28_01 updates.

We expect Microsoft to issue a patch on this as soon as they can.

Update:

 Trend Micro now has a description for the Trojan that exploits this unpatched vulnerability
 
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December 28, 2005 - Posted by | Administrative

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