Microsoft is opening up its Windows Live platform to allow users to share their contact lists with five social-networking sites, some of which until now have been accessing such data through the back door.

The move is intended to give users control of their data, and remove the need for the kind of work-around used to share such data today, "which unduly puts customers at risk for phishing attacks, identity fraud, and spam," wrote John Richards, director of Microsoft's Windows Live Platform, on the official developers' blog for the platform.

Facebook and Bebo members can now invite friends on their Windows Live contacts list to join their online social network at those sites, without having to hand over their Windows Live password. Members of the Hi5, LinkedIn and Tagged communities will be able to do so "in the coming months," Microsoft said.

In return, Windows Live users will be able to invite friends using the five social-networking sites to join them on Windows Live Messenger in a similarly secure fashion through the Invite2Messenger website, Microsoft said.

Yahoo already operates a similar service with LinkedIn: a page on the LinkedIn site takes members wishing to import their Yahoo Mail contacts list to a Yahoo log-in page in order to authorise the data exchange.

Some social-networking sites already offer to help their members import their contacts list from Web-based email services and send invitations to people on that list - but to do this, the sites typically ask their members to hand over the username and password for their webmail account to gain access to the contact data.

That's the case, for example, with LinkedIn's functions for importing contacts lists from Google's Gmail and AOL's webmail service, which require that members trust LinkedIn with their username and password for the other services. LinkedIn does not yet have a link with Windows Live.

Internet users are becoming increasingly suspicious of such requests for credentials, given the prevalence of phishing attacks and other attempts at identity theft.