Spammers have found a way to mine free Web-hosting services for cash.

Online scammers have long used free hosting services such as Yahoo Geocities or Tripod as a way to get around e-mail filters that might otherwise recognize their spammy Web sites. But now some enterprising spammers have begun selling each other these free Web pages, according to security vendor McAfee.

For US$25 per week a spammer will sell 50 Web-hosting accounts that can be used to redirect Web traffic to sites that normally would be flagged.

"These 'link providers' create and maintain thousands of free hosting accounts on behalf of the spammers," wrote McAfee's Nick Kelly in a recent posting to McAfee's Avert Labs blog. That posting can be found here: http://www.avertlabs.com/research/blog/?p=88

"They know that the bigger hosts are unlikely to get blacklisted because they have so many legitimate users," he added.

Scammers also use the free Web pages to try to manipulate search engines, by making it look as if their Web sites are widely linked, said Adam O'Donnell, senior research scientist with Cloudmark, an e-mail filtering company.

And while the free hosting providers are taking steps to shut down this abuse, they appear to be fighting a losing battle.

In late June, Cloudmark researchers were seeing about 1,500 phony URLs (uniform resource locators) on any given day on one of the most abused free hosting services (O'Donnell declined to name names). One month later, that number had jumped to 3,500.

Spammers are simply able to out-pace the hosters' security teams, O'Donnell said. "They will gain more hosts for their pages than the company is able to take down," he said.

The free hosters have been placed in a tough position because they do not want to shut down legitimate users, but they also do not have the technical resources to mine spam for Web pages that are being misused, O'Donnell said.

Lately, however, the hosters have been partnering with security vendors to address the problem.

Cloudmark is working with some hosting providers, hoping to sell them "reputation" information that tells them how many times their member URLs are being seen in spam.

McAfee has been providing similar information to an undisclosed service provider, Kelly wrote. "This relationship has cut the abuse observed by us on that provider by over 90 percent in less than a week."

He added, "let's hope those spammers are buying their new watches from pound$hop rather than Bolex this summer."