in the place where I was working, been observing that these bots actually did not have any owners in the first place. They just was deployed and left behind, automatically scanning the internet for forums and trying to create lots of dummy accounts until the database is too big and eventually becomes inefficient.
my job was to clean up that mess, but when it comes to the database.. it was just a lot of hassle, it would be just easier to remove the accounts being made then placing back only the accounts that frequently posts here on this forum (the regulars), then with the new added security, recaptcha or we can make a few page quiz about general knowledge of Maaya's songs (like what was she popular for etc) so that the bots could never understand nor could guess, unless the person registering was indeed a fan)
Might need to tinker into the php a little, like customizing it. Usually that will works.