Add Excel to trend of spam attachments

Israel-based Commtouch said Monday it is tracking a new trick in which spammers send messages with Excel attachments that contain the latest pump-and-dump stock scams.

"Excel is a natural progression after the recent spate of PDF spam, which itself is a natural development from basic image spam," said Amir Lev, Commtouch’s chief technology officer.

Packaging spam in file formats is successful because it helps the messages evade filters, Brian Azzopardi, senior business analyst with anti-spam vendor GFI Software, told SCMagazine.com.

"Most of the spam solutions don’t really handle attachments very well," he said. "They don’t actually analyse the contents."

The file-format tactic also combines a social engineering aspect, lending credibility, Azzopardi added.

"People are used to receiving these types of documents," he said.

Lev said he expects spammers to continue with this technique, potentially using PowerPoint or Word documents to package the unwanted mail. Attackers already have used Microsoft Office  as a vector for malware that exploits vulnerabilities.

Experts suggest organisations contact their anti-spam vendor to ensure they offer support against PDF and Excel spam. As an alternative, administrators can block attachments or place restrictions on allowable sizes in hopes of weeding out the unwanted mail, Azzopardi said.