Trojan-Downloader.OSX.Flashfake.ab

Technical Details

A family of malware for Mac OS X. The first versions of this type of threat were detected in September 2011. In March 2012 over 600 000 computers worldwide were infected by Flashback. The infected computers were combined in a botnet that enabled cybercriminals to install additional malicious modules on them at will. One of the modules is known to generate fake search engine results, displaying false results for users and generating profits for cybercriminals via ‘click fraud’. It is quite possible that, in addition to intercepting search engine traffic, cybercriminals can upload other malicious modules to infected computers – e.g. for data theft or spam distribution.

A Trojan program that downloads other malicious programs from the Internet and launches them on a victim machine without the user’s knowledge. The program is a Mac OS X (Mach-o) application. It is between 19,384 and 200,876 bytes in size. It is written in C++.

Payload

Once launched the Trojan attempts to upload additional malicious modules. Every 24 hours the Trojan tries to connect to 30 sites, generating 5 domain names while a further 25 are contained in the body of the malicious program itself. One of those sites (randomly chosen) hosts the botnet’s C&C server as deployed by the cybercriminals. The domains have names such as:

jobijoolkfip4oasdkf.com
ithfmmcoo400dmsddditofdl.com
utu9nnmkrogjfldoritvz.com
999rjjfnvmvciwepoqwejdsadkf.com
ighrueokdhfcnnsjwwqqllxz.com
itgii5fmmjmsppperujvmsdkkff.com
jtierodoxzwerkolun.com
iruifjckdlfqwexzcnvdkffd.com
all-nightmexicansoftstore.com
callmetonight911.com
oversellingresourcestoday.com
fasttrackanddeliverytoyourdoors.com
trustedsoftappstore.com
fantastischappstore.com
megastoreappsstore.com
catholicappstorecloud.com
bestcatholicianappstoretoday.com
onlinesoftstoreofweekend.com
knockoutpricesappstoreeveryday.com
svupsvc.com
ajovgdekxrmw.com
ggatocowtonwpn.com
wxsrnrskapelhy.com
ouspjintgjsrw.com 

The Trojan saves the downloaded modules in the following application folders:

/Applications/Safari.app/
/Applications/Firefox.app/
etc.

The downloaded files can be encrypted with the victim machine’s UUID. If loaded successfully, the Trojan sends a notification to its owners at the addresses:

http://adobesoftwareupdate.com/counter/
http://78.46.139.211/jcounter/    
etc.