In the closing months of 2006, the volume of spam jumped enormously, according to e-mail filtering firm Postini, with an increase of 73 percent in just the three months leading up to December.

Spam now represents nearly 93 percent of all e-mail throughout the world -- the highest level ever recorded by Postini -- further driving the need for businesses to find solutions.

An Image Problem

The type of spam being sent has also changed, said Dan Druker, spokesman for Postini. In 2004 only a tiny percentage of junk e-mail messages contained images in them. Now, said Druker, that figure has ballooned to 25 percent.

McAfee Avert Labs says that number is even higher, suggesting that up to 40 percent of all incoming mail is now image spam. A year ago image spam accounted for less than one percent of the total spam received, the company reports.

Although many spam filters are deployed by companies, few are able to successfully defend against spam that is comprised of an image rather than text.

"A lot of spam is in the form of images and HTML documents that are designed to get beyond the filters," said Druker.

"Because spammers are hijacking personal computers and stealing bandwidth to send an unlimited number of spam messages at virtually no cost, businesses can face an escalating series of expenses to ensure their email remains a viable and productive tool," Druker explained.

IM Attacks

Although image spam is in the spotlight these days, it is spam coming through unexpected communications channels that has the potential to wreak the most havoc.

Postini said there has been a dramatic surge of instant messaging (IM) attacks in just one month (160 percent), with new IM threats expected to continue throughout the year.

Postini also saw a significant jump in "directory harvest" attacks, which attempt to steal e-mail addresses from corporate servers coupled with increased activity around the world.