In our monitoring of the GAMARUE malware family, we found a variant that used the online code repository SourceForge to host malicious files. This finding is the latest development we’ve seen since the increase in infection counts observed last month.
SourceForge is a leading code repository for many open-source projects, which gives developers a free site that allows them to host and manage their projects online. It is currently home to more than 324,000 projects and serves more than 4 million downloads a day. Its popularity among programmers and users is the perfect venue to make these malware available to users.
GAMARUE malware poses a serious risk to users; attackers are able to gain complete control of a system and use it to launch attacks on other systems, as well as stealing information. Among the most common ways it reaches user systems are: infected removable drives, or the user has visited sites compromised with the Blackhole Exploit Kit.
This attack is made up of four files. The first is a shortcut, which appears to be a shortcut to an external drive. (This is detected as LNK_GAMARUE.RMA.) Instead of a drive, however, it points to a .COM file (detected as TROJ_GAMARUE.LMG).
The .COM file runs another executable file, which has been disguised as a desktop.ini file. This third file (detected as TROJ_GAMARUE.RMA) decrypts the main GAMARUE file, which has been disguised as a thumbs.db file. The main GAMARUE file (detected at WORM_GAMARUE.LJG) is decrypted and saved in a folder under the Windows directory.
Figure 1. GAMARUE Infection Chain
Once the executable file is decrypted, it downloads updates to itself, as well as malicious files from a SourceForge project. In effect, it uses SourceForge to unwittingly host malicious files.
SourceForge User Serves More Gamarue Variants
The malicious files in the above example were hosted under the tradingfiles project. The same user created two more projects that were also used to host malicious GAMARUE files: ldjfdkladf and stanteam. New files were uploaded in these projects from June 1 onwards.
As we noted in our 2013 predictions, legitimate cloud providers are likely to come under attack this year. A site like SourceForge is a perfect target to be abused by cybercriminals.
Trend Micro protects users from this by detecting and deleting these GAMARUE variants. We’ve contacted SourceForge so these files can be removed from their servers as soon as possible.
With analysis from Threat Response Engineer Lenart Bermejo