Image spam, which is designed to foil automated text-based spam filters, has proved to be so successful that its use has risen dramatically, security experts at Symantec Corp. said today.
It now accounts for an average of 35 per cent of all spam on the Internet, says Symantec's monthly State of Spam report for January. The total number of image spam messages rose from about 30 per cent in July, 2006, to about 39 per cent in December
Moreover, spam in all its forms continued to account for a high percentage of all e-mail traffic, peaking at 80 per cent of messages sent in December.
Spammers have also started using a technique called CAPTCHA with image-based spam. CAPTCHA — Completely Automated Public Turing Test to Tell Computers and Humans Apart — tries to identify if the user is human or an automated process. It is a legitimate tool, used widely on websites to prevent unwanted access by automated programs.
Users who have seen a series of wavy lines in the form of letters and numbers and been asked to retype the characters have used CAPTCHA. The wavy lines are an attempt to defeat optical character recognition (OCR) technology.
The technology creates randomized text with distorted characters that can be identified by humans, but are intended to not be recognizable by computers.
