Researchers and IT managers confirm security vendors' claims that spam levels have spiked in the past month – some say by as much as 80% – and show no signs decreasing.

"There are enormous amounts of spam; it's shot up like crazy since the beginning of October," says John Levine, president of consulting firm Taughannock Networks and co-chair of the Internet Research Task Force's Anti-Spam Research Group.

"Earlier this year, I was seeing about 50,000 spam messages a day, now I'm seeing 100,000."

But a new breed of image spam, where email messages with text embedded in an image file, are evading spam filters, which can't recognize the words inside the image.

US-based hospital network, North Shore-LIJ Heath System has experienced an 80% increase in spam received in the last 45 days, most of which was image spam.

"We got slammed with a 50% increase [in spam] in one day,” said the healthcare provider’s system architect Steve Young. “For the past year-and-a-half none of my users ever got a spam message; in that first 48 hours [of image-spam blasts] there were 500 calls and over 1,000 complaints from users," he says.

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.