Spoofed RapidFax alert carries hard-to-detect Trojan

Malicious email alerts purportedly being sent by RapidFax, a service that allows users to send faxes online without the need for a fax machine, have been hitting inboxes in the last few days, warns MX Lab.

The spoofed “From” email address is reports@rapidfax.com, and the subject line contains variations of “RapidFax: New Inbound Fax”. The body of the email states that a fax has been received, and gives information on when it was received, how many pages it contains, etc.

The email also contains an attachment which supposedly contained the sent fax.

“The attached ZIP file has the name rapidfax-E4C935577EDD.zip and contains the 117 kB large file RapidFAX_MCID_000_LOTS_OF_NUMBERS__13341.pdf.exe,” shared the researchers.

The extremely long name is there to make the .exe extension less noticeable, and the file sports a PDF icon for the same reason.

The file is actually a Trojan, and when the malicious spam campaign was first spotted, the malware was detected by only 2 of the 46 AV engines used by VirusTotal. That number has now risen to 24, but that’s still just a little over half.