image spam

[sosi]

A new way for cybercriminals to lure users into clicking obfuscated URLs. With image spam the obfuscated URL is hidden in an image rather than text making it more difficult to detect.

 

[sesilia]

Image spam is a kind of E-mail spam where the message text of the spam is presented as a picture in an image file. When introduced by spammers most graphical E-mail client software would render the image file by default, presenting the message image directly to the user, it was a highly effective at circumventing normal E-mail filtering software.
The basic rationale behind image spam is that it is difficult to detect using spam filtering software designed to detect patterns in text in the plain-text E-mail body. Attempts to filter text in image spam are easily defeated because optical character recognition of text in image spam can be prevented using a variety of obfuscation techniques which will not prevent the spam image from being read by human beings. This is the same phenomenon exploited by CAPTCHAs, but put to the ends of spammers, rather than to deter their activity.
Obfuscation techniques can include:
Blurring of text outlines
Construction of the image from multiple image layers assembled within an HTML e-mail
Use of animated image formats
Random noise added to the image (also known as confetti) to prevent the detection of multiple similar images using hash algorithms