News 

Ralf Iffert, a researcher at IBM's ISS X-Force threat analysis team, claims PDF spam came onto the radar in early June. By the end of the month, this type of spam accounted for 4% of all junk emails. By the first week of July, that

ADVERTISEMENT

figure had risen to 6-8%.

Iffert claims soon after the first PDF spam was identified, another email was sent containing different attachments, with the PDF containing a single image of text written in wavy lines - characteristic of image-based spam.

"By the current small trickle of activity, it's obvious to us that spammers are simply experimenting with the technique now," says Iffert. "However, as you have probably seen in your own inbox, they are having some success."

"If PDF spam evolves like image-based spam did, then we have to prepare for the possibility that PDF spam could account for 20 per cent or more of all spam," he claims. "In fact, we may see this kind of volume increase happen much faster than the two-year rise of image-based spam."

But there is a glimmer of hope in that the PDFs are identical at the binary level, which means that a signature could be developed to counteract this threat.