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The last time a significant ZeuS/ZBOT development cropped up in the threat landscape, a new ZeuS-LICAT variant was identified. It was also not too long ago when news of a possible merger between the creator of ZeuS and SpyEye made headlines. This time, it is interesting to see an earlier version of the notorious malware recently making its rounds online.

A spammed message, purportedly from the Executive Office of the President of the United States, spreads holiday cheer with a message and links to what is supposedly a greeting card. Clicking the link, however, leads users to a website injected with malicious iframe tags, which Trend Micro detects as HTML_IFRAME.SMAX. Viewing the malicious HTML page leads to the download of a .ZIP file, which contains the malware detected as TSPY_ZBOT.XMAS.

This particular variant exhibits routines that ZeuS version 1.x are known for. Apart from the typical information theft routines, it modifies HOSTS files to prevent affected victims from accessing antivirus-related websites. The technique of using important events to lure potential victims to open the spammed messages is not new either. While some targeted victims may have an idea that the these types of messages may be malicious, some people simply rely on their antivirus programs. The cybercriminals behind this attack took advantage of this fact by ensuring that the file was heavily packed and was not yet detected by most antivirus programs, leaving unknowing users vulnerable.

Trend Micro customers are protected by the Trend Micro™ Smart Protection Network™,  which detects and blocks the malicious components of this threat.

Special thanks to threat analyst Edgardo Diaz, Jr. for initially bringing this threat to light and to anti-spam research engineer Mary Aquino for the spam sample analysis.