Spammers have now gone back to a years-old tactic of using images for their messages, a security researcher warned.
Image spam had its peak in late 2006 and early 2007, and was successful at slipping through filters, which were designed only to parse text and look for such things as links. However, it's surprising it is coming back, as spammers know that anti-spam vendors have already figured out how to detect that type of junk mail. Nevertheless, image-based spam accounted for about 25% of all spam at the end of last month.
One of the differences this time said, Holly Stewart, the threat response manager of IBM Internet Security System's X-Force team, is the content of the image spam. Today most of the image spam is focused on drugs and pills, whereas, before it was "stock 'pump-and-dump'." Another reason, she said, is that few of the messages included ready-to-click links, with most of the images containing a URL that the user has to type in manually.
It is also known that spammers conducted an image spam test from about March 19 to April 9, according to X-Force's, which showed a spike in the tactic. Which obviously was successful, as after a short period of disappearing entirely the tactic came back on April 21.
Steward warns that the return of image spam could be the first resurrection of other once-popular tactics, such as MP3 spam and PDF-based spam, both of which were popular in 2006 and 2007.