Microsoft Excel has become the latest vehicle for carrying stock pump-and-dump spam scams, according to US security specialist Commtouch Software.

First identified and blocked by Commtouch on 21 July, the Excel spam promotes stocks in file attachments with names like "stock information-3572.xls," "invoice20202.xls," and "requested report.xls."

"Excel is a natural progression after the recent spate of PDF spam [1], which itself is a natural development from basic image spam," said Amir Lev, Commtouch's chief technology officer. "We expect other file formats to follow suit; think of the spam potential in PowerPoint files, or Word documents."

Spammers may assume that by wrapping the same message in a new format, they will bypass most anti-spam engines that try to analyse the content of mail messages.

Like other types of spam messages, the Excel spam is being sent from zombie computers or "bots," typically home PCs that have previously been infected by Trojan horse viruses. Spammers control massive numbers of machines in vast "botnets" that they link to launch global spam and malware outbreaks.

Malware writers have used Excel in the past as a carrier for viruses, for example in a series of attacks during June and July 2006 that exploited vulnerabilities in Microsoft software, including Excel, Microsoft Word, and PowerPoint.

This article first appeared on our US sister site, AccountingWEB.com [2].