Network Computing is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Spam Volume Jumps 35% In November: Page 2 of 3

Spammers are using malware development tactics such as trying out new strains of spam in limited quantities to gauge how effective they are against filters, then sending out huge quantities only when they're sure a good number will slip through defenses.

"They're doing test runs to see what the returns are," says Mayer, "and to see how many messages bounce back from invalid addresses. Only then will they send out the [spam] blast."

Scammers have been able to turn up the spam volume because of the seemingly limitless number of systems vulnerable to hijack, using an individual bot for only hours to send out large quantities of spam, then discarding that PC to move on to another. The volume, along with the constant tweaking they give to their messages, means that at times traditional rule- or blacklist-based anti-spam defenses can be overwhelmed.

In mid-November, for instance, IronPort monitored a new, large-scale spam attack that dropped filter efficacy by more than 10 percentage points, letting millions of messages through to in-boxes.

"It's a reaction gap," says Mayer. "It takes time for vendors to respond and come up with appropriate rules, but with their distributed [botnet] networks, spammers can send a huge attack in a matter of hours. It takes time for anti-spam solutions to catch up with the attack."