psychonaut13
New Member
found this on a design board that i'm a member of.
I felt this was important enough that everyone needs to be aware of this that is an Announcement for now.
http://www.securityfocus.com/brief/89
WHAT IS IT?
There is a new exploit out that uses WMF (windows metafile format) files to infect a computer. All you have to do to get infected is view a webpage that has the image on it, or access an infected image that is on your computer. That means the forums can be a vector for infection too. (In fact, user Blue Reptile has already been permabanned for putting the exploit in his signature.)
WHO IS VULNERABLE?
The exploit affects Firefox, Internet Explorer, and any other browser that displayes or downloads the file into the cache on the local machine. The file could also be a WMF renamed to any other image type, or possible other filetypes. Anything that puts the image exploit onto your computer or opens it up in windows fax viewer or the part of windows that generates thumbnails of WMF files is a vulnerability. This means any vector that puts the image onto your computer (wget, browser, email, IM, etc) can potentially cause the problem.
This affects anyone on Windows (98, 98SE, ME, 2000, XP, 2003). USING FIREFOX DOES NOT ELIMINATE THE RISK as the file is still downloaded to your cache in most cases, but it does reduce your chances somewhat since the image is often not displayed in the browser. But if you then interact with the file in any way (thumbnail it, Google Desktop, hover over with the mouse) that causes it to be handled by the windows subsystem responsible for WMF then you will have problems. Once again, YOU CAN BE CAUGHT BY THIS EXPLOIT EVEN IF THE IMAGE DOES NOT SHOW IN THE BROWSER. If you use Windows, your system is vulnerable.
WHAT DOES IT DO?
The exploit can be used to drop viruses, trojans, installers etc onto your computer when the exploit is activated (when the file is parsed by the part of windows with the problem). It does not do anything by itself until it is activated. There have been several reports of trojans being downloaded, which then download other things, other spyware, etc. Some of these are "SpyAxe", "AYL" trojan downloader, "ASC" trojan, and other stuff. Here's a video of what this version is doing:
http://www.websensesecuritylabs.com...s/wmf-movie.wmv (thanks Merijin).
WHAT YOU CAN DO TO HELP PROTECT YOURSELF
1. SCAN YOUR COMPUTER - NOD32 TRIAL VERSION is a good one. Update the definitions right away after installing - they auto-update but you want to be sure you have the latest. (Your goal is to have an antivirus software with a realtime scanner that detects the exploit itself, and not just the payload that it drops. NOD32 does this, at least for this variant.)
Even if you think you are safe, scan your Windows computer anyway. ClamWin appears to catch this, but it doesn't have a realtime scanner. SAV Corporate 10.2 does not catch it outright (the bloodhound heuristics may) but Symantec's own site says that it possibly may never work fully for this due to something about how the virus works. AVG, McAfee, Trend are unknowns at this point. I have personally tested NOD32 and found that it's AMON on-access scanner stopped the image as soon as it was saved to the cache, before it was able to execute anything. NOTE: SCAN ALL FILES. Some AV solutions only scan "infectable" files and do not scan image files because the program thinks they are safe. Check for an option to scan all file types and make sure that is enabled.
UPDATE: Most AV companies should have definitions updated by now, but check to be sure that they protect against the actual exploit itself, not just against whatever trojan the exploit drops on the computer.
2. USE AN ALTERNATIVE BROWSER - Using Firefox or an alternative browser will reduce your risk because it does not display the image. However the image is still downloaded to your cache, and some browsers prompt you to open the file - which you should not do!
3. TURN OFF SALR's feature that makes text links into images. If you have that feature turned on, someone could make just a text link that displays the infected image in your browser.
4. TURN OFF GOOGLE DESKTOP or anything else that does indexing of files on your computer.
5. USE COMMON SENSE - Don't go to links you don't trust, don't open files you aren't expecting, including suspicious email or IM's, etc.
6. KEEP ON TOP OF WINDOWS UPDATES - Hopefully they can fix this one quickly, but you really should be up-to-date on everything else anyway.
7. AVOID IMAGE SEARCHING and visiting webpages you don't trust. Some of the places this image has been popping up are: eBay XBOX auctions, porn sites, google image search, wikipedia, myspace, other forums, etc - places where people can post their own images. If you have a competent realtime scanner that can catch the image before it executes anything you are ahead of the game here.
BONUS TECHY STUFF
8. You can try unhooking the part of Windows that views those image files. To do this, click Start -> Run and type regsvr32 /u shimgvw.dll then press OK. You will get a confirmation message. To undo this, repeat but type regsvr32 shimgvw.dll instead. Note: This only has a minimal benefit - it only disables the image viewer itself. It doesn't prevent against viewing the exploit image in Internet Explorer, for example. Messing around with this is at your own risk
BOTTOM LINE: If you use Windows, you will not be 100% safe from this exploit until the problem in windows is patched - there is no official patch yet.
Does NOT execute when:
* the WMF is viewed inlined (i.e. <img src="exploit.wmf"> )
* the WMF is renamed to another filetype/mimetype and viewed standalone or inlined in IE (opening up http://example.com/renamedwmf.jpg in IE will not affect you even if they have JPG's set to a WMF mimetype)
DOES execute when:
* viewed standalone in IE (opening up http://example.com/exploit.wmf)
* thumbnailed or viewed in Explorer or XP's builtin picture viewer, regardless of extension (saving a renamed exploit.wmf as exploit.jpg then attempting to view it will get you)
Protection
Not foolproof, but your best bets until a patch is released are:
Use a non IE browser. (1.0.6+ of FireFox will at least prompt to save/open if you download an infected file from the web, IE automatically loads up Picture & Fax viewier, executing the exploit).
Don't save and open untrusted image files.
Use up-to-date antivirus that detects the exploit (NOD32 - http://www.eset.com)
Disable explorer thumbnail/autoparsing of images (explained here)
Any other app that indexes your hd can trigger the exploit when it touches an infected file (Google Desktop indexing your temp internet files for example).
Processors that support DEP / noexecute in hardware seem to stop this cold. (confirmed on AMD64 and Pentium D with DEP turned on for all programs and services) - there are ways around DEP, but it should stop almost all variants.
