Our post last week warned on a group moving their FakeAv-Koobface-Vundo-Spyware “softwarefortubeview” phony codec downloader to a new home last week, and this week, we are examining a similar scheme that downloads, surprise, surprise, Koobface, FakeAv prompting BHOs like iehelper.dll’s prompts for “Antivirus system PRO”, performs some level of click fraud, installs podmena.dll and podmena.sys…this one also includes a nice ftp credential stealing component, stealing passwords from FileZilla, Coffee Cup, FTP Control, CuteFtp and more.

Streamviewer.40050.exe (and other streamviewer + random version names) has been flying off the shelf at a server on 64.20.38.171. That ip hosts multiple badware domains:
go-exe-go.com
reverse38-170.reserver.ru
gruzzilla.com
hot-exe-area.com
last-exe-portal.com
main-exe-home.com
super-exe-home.com

Interesting about the downloader is the way in which additional malware is downloaded and dropped by this phony codec. It contacts a set of servers with encoded data about the system.
reportsystem32.com (216.240.146.119)
terradataweb.com (66.199.229.229)
dvdisorapid.com (64.27.5.202)
superimagesart.com (95.211.8.61)
thenewpic.com (66.148.80.4)

It then pulls out data from a decoded xml file containing a list of urls to contact for a variety of .gif images (titem.gif, qwerce.gif, 217.gif, etc).
superimagesart.com
thenewpic.com
stockshopimages.com
imagesoffline.com
theimagesphoto.com
imageheadphones.com

At the time of download, gif viewers will display titem.gif with a political message about french politician Christine Boutin:

Know that we do not endorse any political message with this post. But this gif image is no ordinary image. If it were, its size might reach 35 kb at the most. Embedded in the image is the encrypted payload, bloating the image out over a couple hundred kilobytes (~270 kb).
The downloader gathers the response information from the previous sites to find more urls to contact and finds its decryption key. It then uses its key to decrypt the code embedded within downloaded gifs.

Much like the recent (and possibly related) beladen downloader and the older Tibs downloaders, this malware delivery embedded image scheme attempts to evade gateway appliance based protection and optimized AV scans with gif-based encrypted payloads. It stymies automated web crawling based research efforts. No longer are we seeing simple xor decoding schemes with visible PE headers in downloaded image files. The encryption implemented for this attack was another previously commerical and proprietary encryption algorithm.
ThreatFire is preventing this downloader in fairly high prevalence.

This entry was posted on Tuesday, June 16th, 2009 at 9:15 am and is filed under Embedded trojan, Evasion technique, Obfuscation, Reversing. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.