How to ban a user?

I had indications of someone hacking in and registering to a course for $1 instead of the full price, and then downloaded everything she could. Darn, this time, i wish s2M didn`t work correctly, and didn`t give immediate access. Anyways, i was able to trace her route, got her IP and such. I revoked her level 1 but i dont want to delete her user so i can keep it as record, but i want to ban her. How would i do that? Any idea?