Commtouch has released its Email Threats Trend Report for the third quarter of 2007 (pdf file), based on the automated analysis of billions of email messages weekly. The report examines the appearance of new kinds of attachment spam such as PDF spam and Excel spam together with the decline of image spam, as well as the growing threat of innocent appearing spam containing links to malicious web sites.
According to this report, global spam levels reached an all-time high of 95% of all emails at its peak during the quarter. PDF Spam represented 10-15% of all spam in early July and then dropped significantly, however a steady stream of PDF spam is still being maintained at 3-5% of all spam messages. Moreover, pharmaceuticals and sexual enhancers were the most popular spam topics, at 30% and 23%, respectively.
One technique which reached a new high during the quarter was innocent-appearing spam messages that contained hyperlinks to malware-sites. Several blended spam attacks of this type focused on leisure-time activities, such as sports and video games. Messages invited consumers to download “fun” software such as NFL game-tracking and video games from what appeared to be legitimate websites.
Spammers experimented with several new techniques to slip past anti-spam engines and into inboxes throughout the quarter. For example, they disguised messages in PDF, Excel, and other popular file formats. This simple trick fools many anti-spam technologies and end users alike, whose guards may be down when they see the popular file attachment ending.
Originally posted on October 16, 2007 @ 9:30 am