Postini study: IM attacks jump sharply

The company filtered 7.6 million IM conversations in April, an increase of more than 15 percent from March's 6.5 million, underscoring the continued growth of corporate IM. Compared to email viruses, which are roughly two to three percent of all email, IM malicious content is relatively low at 0.1 percent of all IM traffic. However, that is an increase of 25 percent from March, when only 0.025 percent of IM conversations were blocked as malicious.

Postini noted that the Mytob virus had a variant that was traversing all IM and enterprise clients. Trojans that were blocked included IMFlood and JahuKit, and worms included Appflet, YahooSpy, Mpass, and MSNFake.

"The continued increase in IM messages by 5.5 million over the past two months is a clear indication that IM is becoming a mainstream business communications tool for employees," said Andrew Lochart, senior director of marketing for Postini.

According to the analysis by Postini, based on monitoring over 22 billion messages last month, unwanted email accounted for 18.5 billion messages, a one-percent decrease from March. This brought the total amount of unwanted email to 84 percent for last month.

Postini measurements show that TLS (Transport Layer Security) encrypted message volumes remained steady at seven percent of legitimate email.

While IM attacks were on the rise, the number of quarantined viruses remained the same as March, with the firm stopping a total of 28 million viruses.