It is the admin doing it, it's been going on since last night. He's exploiting a feature that allows him to mass follow remote accounts.
@fsnk yea but to what end?
@freemo I don't know. Dumbassery?
Skimming their timeline it looks like it started as a way of artificially boosting follower count for specific accounts, and then he got the bright idea to try and DOS smaller servers. There's an open issue:
@fsnk As far as a Dos goes it was kinda lame. Didnt even register on our servers
@freemo @snder
The admin himself created those Accounts, They started flooding our server with follow requests.
We blocked them.