Image-based spam has grown dramatically in the last year from 1% of all spam in June 2005 to 12% this year, according to Internet security firm IronPort Systems.
More than five billion image-based spam e-mail messages are sent per day, the company said. Spammers are increasingly embracing the tactic because it allows them to deliver their messages in an image rather than using text, making it more difficult for spam filters to detect and block them, IronPort said.
Spammers are also increasingly using “zombies” or hijacked PCs to deliver their messages, the company said. More than 80% of spam now comes from zombies, usually computers owned by unsuspecting consumers in broadband networks, the company said.
According to IronPort spam volumes surged more than 40% worldwide from April to June.
Spammers are also exploiting the domain name registration system by registering domains for a short period of time and then letting them expire before paying for them, according to IronPort. In April, there were over 35 million domains registered, 32 million of which were never paid for and expired after five days, IronPort said.
“This effectively brings the cost of registering a domain to zero for spammers, while overwhelming traditional URL blacklists that can't update their lists fast enough to keep up with the surge in new domains,” the company said.
