Windows Live SkyDrive Beta, Microsoft's free online storage and file sharing service, appears to be taking off... with spammers.

McAfee security researcher Chris Barton on Tuesday reported, "Our labs trapped many thousands of spam overnight that are abusing the Windows Live SkyDrive Beta service..."

Windows Live SkyDrive Beta is part of Microsoft's Windows Live portfolio of services. It was launched last August under the name Windows Live Folders and later re-branded. In October, the service was updated and it now offers users 1 Gbyte of free online storage.

The spammers appear to be uploading single-line HTML files that redirect Web visitors to a Web site used to sell spam-promoted products, such as pills of dubious value and function.

There are two main advantages to this approach, which is similar to adding spam links to "splogs," as spam-saturated blogs have come to be known. First, Microsoft's domain is unlikely to be blacklisted. And second, there's no hosting cost.

"We've seen a few small scale spam using the SkyDrive service dating back to November last year but [those] were on an much smaller scale to last night's campaign," observed Barton. "I'm sure it won't be too long before it's used to host other unwelcome content types."

Barton suggests that online storage services should make more of an effort to scan for malware.

Windows Live SkyDrive specifically prohibits use of the service that "intends to harm or disrupt another user's computer or would allow others to illegally access software or bypass security on Web sites, or servers, including but not limited to spamming."

Barton characterizes Microsoft's Code of Conduct for the service as "pretty good," but it's not clear from that wording of the prohibited uses whether spamming that intends to sell, rather than harm or disrupt, will be tolerated.