Steam, the online gaming network run by game company Valve, confirmed Thursday that its forums had been hacked and warned users to keep a close eye on their credit card statements.

The service’s forums had been defaced earlier in the week, resulting in some gamers receiving e-mails from a hacking Web site, Kotaku reported.

On Thursday, Valve co-founder Gabe Newell left a message on the company’s forums confirming the intrusion, saying that all forum passwords will be reset and adding that the attack “goes beyond the Steam forums.” While there is evidence of a deeper intrusion, the company is not yet requiring all Steam users to reset their account passwords, which are separate from forum accounts.

“We do not have evidence that encrypted credit card numbers or personally identifying information were taken by the intruders, or that the protection on credit card numbers or passwords was cracked,” Newell wrote. “We are still investigating.”

He added that there have been no reports that Steam accounts were compromised, but advised users to change their passwords as a precaution.

“I am truly sorry this happened, and I apologize for the inconvenience,” he said.

The intrusion comes at a bad time for Steam, which is not only premiering a major title — Bethesda’s “Elder Scrolls V: Skyrim” — Friday, but is also facing long-term challenges from Electronic Arts’ Origin service, cloud gaming service OnLive and an as-yet-unreleased online service from retailer GameStop.

Security, understandably, is the most pressing issue facing these services as they ask gamers to trust their saved data, credit cards and other personal information to off-site servers. Companies are also jumpy following the Sony data hack that pulled the PlayStation Network and Sony Online Entertainment services off line for a month and resulted in a lot of bad press for the electronics giant.

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