A naughty hacker has busted into the database of S2's Heroes of Newerth, gaining access to account login information. If you've played the DotA 'em up and use a password shared with any other online account, you'll want to get to changing those passwords and, honestly, start using individual passwords for each account.
"At 2:30 PM EST we became aware that a Heroes of Newerth password security breach had occurred," S2 Games says in an announcement on the in-game login screen. "We encourage everyone to change any passwords that were shared with your Heroes of Newerth account. Do not change your Heroes of Newerth account password at this time."
S2 has brought the servers down in response, so for now you can't get your HoN on.
If the rash of gaming hacks over recent years hasn't convinced you to start using individual passwords and a password manager like KeePass, well, you really should.