Spammers have started abusing Microsoft's Windows Live SkyDrive service to host spam links, a security firm warned today.

McAfee Avert Labs trapped thousands of spam messages at the start of this week which included a link to the Microsoft service.

Clicking on the link redirects unwitting surfers to an online pharmacy service.

Windows Live SkyDrive is an online storage service launched in beta in August. Users can upload and share files with anyone via web links.

This latest spam campaign saw an HTML file uploaded with a redirect to an online pill store.

McAfee estimates that the spammers uploaded "tens of thousands" of such files to the Microsoft service.

"Services like Windows Live SkyDrive are attractive to spammers for a number of reasons," said Chris Barton, lead anti-spam researcher at McAfee Avert Labs.

"These services are free, they provide unique long-lasting web links, they host almost any kind of file and are relatively safe from blacklisting."

Spammers are regularly turning their attention to online services, including storage services and blogs.

McAfee Avert Labs recommends that service providers scan the content placed on their systems to weed out spam and malicious content.