PDF spam on the rise, as spam techniques converge

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Spam with portable document format (PDF) attachments are on the rise, as image spam slows down and spam techniques converge, according to a new study by malware services firm Commtouch. The report, titled, " Email Threats Trend Report for the second quarter of 2007," is based on the company's real-time analysis of billions of e-mail messages globally each week.

It found that PDF spam rose at the end of the second quarter and during one massive attack, PDF spam comprised 10 percent to 15 percent of spam. Meanwhile, image spam dropped to 15 percent of spam, down from 30 percent in the first quarter of 2007. It also noted that spam and viruses have joined forces, using the same botnets to distribute both types of e-mail-borne threats, sometimes even in the same e-mail message.

"We have noticed a convergence of different kinds of threads of spam and malware coming from the same zombie computers," said Rebecca Herson, senior director of marketing at Commtouch. "Just like any legitimate business person, these spammers and malware writers want to make the infrastructure they have built for themselves work for as many things as they can."

Other findings included that global spam levels remain high. Eighty-five percent to 90 percent of all global e-mail is spam. In addition, more than 60 percent of spam-sending bots also send malware. There are more than 300,000 zombie computers, personal computers infected with spam sending malware, become newly activated each day.

The most popular spam topics were to be expected - pharmaceutical represented 45 percent of spam, stock 18 percent and sexual enhancers 10 percent.

To protect themselves, Commtouch advises consumers not to open e-mail that they do not recognize, and not to open attachments from unknown sources.

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