Spammers have long attempted to bypass anti-spam software by incorporating their sales pitch into an image, rather than sending it as plain text. When they first adopted this practice, they were able to evade simple content recognition tools. As image spamming grew in popularity, anti-spam vendors developed signatures designed to detect specific image spam messages. In doing so, the anti-spam software was able to reference these signatures and reject identical or nearly identical messages.
However, spammers have now fired a new barrage of image spam using randomized images that appear identical to the human eye, yet appear to be entirely unique to most anti-spam software. Many of the changes to the images contained within spam messages are so subtle that they require a pixel-by-pixel examination of the image in order to detect the differences.
Read how Secure Computing effectively addresses this problem.