Microsoft has denied reports that users of its Xbox Live online gaming service have had their accounts hacked.
Some Xbox Live gamers have complained about fraud
It follows a number of complaints from gamers that their IDs, or gamer tags, have been taken over while playing.
The problems came to light after security researcher Kevin Finisterre reported his experience of a problem first-hand on his website.
In a statement Microsoft said it had found no evidence of any compromise of the security of Xbox Live.
As well as at least 50 other people complaining on the official Xbox forum about having their gamer tags stolen, Mr Finisterre also found clans (gaming groups) openly boasting about stealing accounts.
Some claimed the information was being extracted from people working for the Xbox Live support service
"One of the first posts said they were not stealing the account details but being given them by Xbox Live support," Mr Finisterre told the BBC News website.
A Microsoft spokesman told the BBC News website that "rumours about accounts being hijacked are false".
In a statement the firm said: "There have been a few isolated incidents where malicious users have been attempting to draw personal information from unsuspecting users and use it to gain access to their Live account.
"We think this is a good time to remind our members that they should never give out any of their personal information."
Mr Finisterre, who started a website in January revealing a different bug in Apple systems each day of the month, said he had believed his account had been affected.
"On Thursday last week I was playing Halo and a gentleman said he was going to steal my account," he told the BBC News website.
The next day he found he had been locked out of his account, with the explanation that someone else was using his gamer tag.
"I phoned Xbox Live support but was given the run-around," he said.
Begging for help
Eventually a conversation with a support agent, which he has recorded and put on his website, revealed that several other Xbox users had called with the same problems.
"They said there was nothing they could do and accused Bungie of being responsible," he said.
Bungie Studios is the Microsoft-owned developer of Halo and Halo 2. Microsoft also denies that the company had been hacked.
Mr Finisterre said he was unimpressed with the way Microsoft's support service had dealt with the problem.
"There are people out there begging for help and they clearly aren't getting it," he said.