Excel Spam Outbreak Launches a New Trend

An outbreak of new Excel spam, which puts textual content inside a Microsoft Excel file, is hitting users' inboxes, according to a recent report by IronPort.

Excel spam attack was first launched on July 21, 2007. It sent messages in an image or text format within Excel file attachments, the malicious ones of course. This new format evolved with the decline of image spam due to strong industry-wide filtering.

Spammers are aiming their attacks just like players in a basketball game, said Dave Mayer, product manager with IronPort, San Bruno, CA in a statement. DM NEWS published it on August 14, 2007. By increasing the number of shots and strategic shots, a player can hit the basket and score a point. In the same way, spammers have doubled the amount of messages from 2006 and have increased the sophistication in their spamming techniques, Mayer said.

Excel spam has come to naturally develop after the flood of PDF spam, which too developed naturally from image spam. spammers think that by putting their messages in the garb of a different format, they would be able to avoid anti-spam engines that work by assessing the e-mail message content.

Just as other kinds of spam mails are sent out from zombie PCs or 'bots', Excel spam also pushes out from compromised home computers that have already been infected with Trojan horses. spammers control enormous numbers of computers in massive 'botnets', which they use to launch malware outbreaks and global spam.

When spam filtering companies and ISPs block one style of spam, spammers use new file formats that are able to bypass the existing filters. Apart from Excel spam, spam with PDF attachments has also been increasing. In just a few hours of unleashing them, Excel and PDF-based spam accounted for a good 17% of all spam mails.

In the past, malware authors have employed Excel as a medium to carry viruses, for instance in the spate of attacks in the months of June and July 2006 when they exploited weaknesses in Microsoft Office suite of Excel, PowerPoint and Microsoft Word.

Related article: Excel Displays Three Holes

» SPAMfighter News - 8/29/2007