Image spam gained prominece as a major vehicle for spam delivery roughly one year ago. At first, most spam filters were ineffective at blocking the image based messages. Since then, image filtering has become more effective and, as a result, spammers have had to continuously alter their images, in some cases making them unreadble. To get around this problem, the spammers are now adopting a new Image Spam delivery technique to bypass spam filters and deliver crisper, cleaner looking images. The new technique works as follows:
- Upload Images to a Legitimate Photo Sharing Site (Flikr, Shutterfly, Picassa, etc..)
- Imbed an image link in the body of the spam message
- The image is downloaded when the message is opened, or, when/if users allow their mail client to download the image
We have not had reports from our clinets that these messages are getting through to them. If you find that these messages are bypassing your filters, the simplest thing to do is to quarantine/deliver to junk mail any message containing a URL from photo sharing sites.