This reminds me of my third most favourite MIT hack:

In 1998, Bill Clinton gave MIT's commencement address.

The MIT administration discovered that a rather embarrassing hack was planned. To forestall it, a few days before commencement, a sternly worded message was emailed around:

Any students who appear at the commencement exercises wearing a black beret, a blue dress, kneepads, or any combination thereof will be denied entrance.

Needless to say, the hack itself was never intended to be performed.