IronPort identifies Excel spam trend

A breakout of Excel spam, a new type of spam sent as text inside a Microsoft Excel file, is under way, according to a new report by IronPort.

Excel spam, which first appeared on July 21, 2007, is typically sent in a text or image format that has been exploited with malware Excel file attachments. The new form has taken shape as image spam has decreased due to the strong filtering industry wide.

"I think that spammers are targeting like basketball players," said Dave Mayer, product manager with IronPort, San Bruno, CA. "By taking more shots and by taking more strategic shots, you are more likely to score a basket. The same goes for spam. Spammers have increased the volume of messages, in fact it doubled in the last year. And they have gotten more sophisticated with their technique."

When one spam style gets blocked by the spam filtering firms and Internet service providers, spammers typically exploit new file formats to get past the filters. In addition to Excel spam, spam with malignant PDF attachments has been on the rise. Within hours of their release, Excel and PDF spam represented as much as 17 percent of total spam volumes.

According to Mayer, spammers could probably design spam with any kind of attachment that is commonly used, such as a Power Point.

IronPort is also currently examining Forms Data Format, a form file spam read by Acrobat and other PDF readers, with stock messaging in the spam.