Image spam blamed for October hike

The majority of these image spam messages are so-called pump and dump scams, where spammers purchase a penny stock, promote it through email, then sell it at a profit. Most appear to come from Europe, said Levine.

Security vendors have responded with products that create a "fingerprint" of the message and match that against new incoming messages. Now spammers are randomising image spam so that each message was slightly different from the last, therefore evading fingerprinting technology.

Levine said, whether or not anti-spam products can evolve fast enough to catch these new spam variants, the increase in unwanted email levels necessitates more bandwidth and computing power for anyone running an email system.

"Spam is huge tax on e-mail, and the tax just doubled," he says.