Looks like the Steam forums have been hacked, forums are down for maintenance atm, and received an email from steampowered.com with the following:
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.
the fkn0wned team.
Looking at the mail headers, looks to be sent directly through steam forums too, and sent to my steam forum contact email (separate to my steam account).