Okay, quick update on this just so people know what's going on.
We've spoken with gromph about this and there's currently no evidence of a breach on NeoGAF's servers. As best we can identify, this has been the result of users' accounts being accessed directly via their password. We're aware of who appears to be responsible (in fairly great detail) and we're doing what we can to mitigate the issue, but we can't necessarily prevent completely people's accounts being accessed using a guessed or brute-forced password.
Since this is coming up, this is a good opportunity to reiterate this: if you reuse passwords or use insecure passwords then your accounts are very likely to be compromised. Please use a unique password on NeoGAF that isn't used on any other sites (since otherwise a password leak on another site can lead to your account here being compromised); pick one that's long (12+ characters) and not based on dictionary words or identifiable personal information. Ideally, pick a random password and store it in a password manager. Everyone should consider this a good reason to change their password today.
I'll note that we're also aware of the issue of accounts registering just to send obscene PMs to other random users, and we're also doing what we can to mitigate that, but it doesn't seem to be connected to this issue.
