Valve's Steam forums are currently offline, and users have accused a hacking group of being responsible.
Eurogamer reports that the email from Steampowered.com was distributed to some users:
"Ever wanted to dominate the servers you play on with guaranteed results, but you were too afraid to cheat because of ban risks? Visit [removed domain] It's safe, secure and undetected.
"Along with hacks, we've also got some general discussion sections, hacking tutorials and tools, porn, free giveaways and much more. This site has been conditioned to meet all your needs in terms of resources so be sure to take a look and tell us what you think.
"Thanks again, the fkn0wned team."
There's no indication of whether any user information was compromised, and whether the forum itself or simply the email systems were the target.