Several Xbox 360 users have complained that their Xbox Live user IDs, or 'gamer tags', have been taken over while they are playing, and that they were unable to log-in to their accounts at a later point.

"Some folks are having their Microsoft points stolen or points purchased via their stolen gamer tag," said security researcher Kevin Finisterre in a posting to the Full Disclosure security mailing list on 19 March. 

The InFamOuS online gaming clan even lists accounts that it has stolen, accompanied by the reason why, Finisterre found. 

An account by the name of 'BxR RaMpAgE' was allegedly stolen because the previous owner "talked s**t to 'JuStCaLLMeFRESH'".

One user on the Xbox Forum claimed to have lost five accounts to the clan. 

Microsoft's helpdesk agent acknowledged the issues to Finisterre but blamed the problems on Bungie Studios, the Microsoft owned developer of Halo and Halo 2. Finisterre has posted a recording of the conversation on his website. 

Numerous users have suggested that Microsoft or Bungie has been hacked. A Microsoft spokesperson categorically denied that the Bungie.net service has been compromised.

"Bungie.net has not been hacked and Xbox Live accounts have not been stolen. Any reports stating that are false," the company said in a statement to vnunet.com.

"Xbox Live has strict policies against hacking and will penalise any individual who attempts to do so."

The Xbox Live service allows gamers to connect to the internet and play online. It also provides access to the Xbox Live Marketplace where users can purchase digital goods such as armour and weapons, or expansions to existing games such as maps.

Purchases are charged with so-called Live Points. Microsoft sells a credit of 4,000 points for $50. Gamers also can link their credit card to their Xbox Live accounts to allow for purchases to be made from within the gaming console.

Microsoft Points are also the currency of choice for the company's Zune Marketplace, an online media store where a single song goes for 79 points. The digital currency cannot be converted back into real currency.

Finisterre is currently collecting reports about stolen Xbox Live accounts in an attempt to force Microsoft to take action.

"I would certainly say that Microsoft is more than negligent in dealing with this issue especially with regard to the potential theft of personal information," he said.