Cyber-criminals use legitimate third-party Web sites and e-mail to cloak spam and malware, says Commtouch.
According to its Q1 2008 e-mail threats trend report, spammers and malware writers use valid Web sites and e-mail messages to bypass spam filters.
The report also found that spam levels ranged between 60% and 94% of all e-mail throughout the quarter.
"Spammers leveraged the high level of interest early in the quarter in mortgages, with mortgage refinancing spam jumping to 10% of all spam at its peak," says Amir Lev, Commtouch CTO and president.
The report shows that holidays continued to be celebrated in spam and malware, with outbreaks in honour of Valentine's Day, St Patrick's Day and April Fool's Day.
Furthermore, on average throughout the quarter, 355 000 zombies were newly activated each day to participate in malicious activity, the report reveals.
"Malicious e-mailers will use any freely available tool to their advantage, including Hotmail, Flickr, Blogspot and even Google and Yahoo calendar tools," says Lev. "Traditional content filtering tools are limited in the ways they can isolate the illegitimate e-mails that cloak their messages in legitimate content, since aggressive filtering will lead to false positives."
More details, including samples of spam and malware messages, are available in the report, available from Commtouch Labs.
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