The vandalism was coming from: 18.56.0.30 and soon after *.31.
That's at MIT, apparently. Drunk college kid, I bet.
I blocked just those two, and things have been quiet for a few
minutes. We might need to extend the ban to 18.56.0.* for a few
days if it becomes necessary.
I'm logging off now, hopefully this information will be sufficient
to allow others to mount an easy defense if it comes back.