Updated 4:30 p.m. PST with latest Microsoft comment.
Some Xbox Live players are finding that winning has its drawbacks.
Microsoft said it is investigating reports that people are using malicious software to disrupt Xbox Live players' Internet connections in malicious attacks.
"In our continued effort to help provide a safer and more secure experience for our community of more than 17 million members, we are investigating reports of a malicious Web site that attempts to lure Xbox LIVE members into providing personal information," Microsoft said in a statement on Friday.
"Phishing is an unfortunate and common threat on the Internet, and this problem is not related to the Xbox LIVE service," the statement said. "We encourage people to only do business with trusted Web sites and never enter personal information on unfamiliar sites."
Malicious software is being used by attackers to do things like temporarily shut down a game player's console or even an entire game with a denial-of-service attack targeting the IP address, according to Chris Boyd, director of malware research at Facetime Communications, the BBC News reported on Friday.
Sophisticated hackers are selling their Xbox Live attack services to others via the Internet underground for as little as $20, the report said.