yes, just filter by MAC and redirect him to meatspin.Do you control the router? If so, just restrict access to listed machines only.
How is their computer affecting you?
He'll just go use your computer when you aren't home and get virus on it
I don't want to be blamed by my ISP for what his computer may be sending or hosting.
Why do you care though?
If his roommate's computer is spamming the web, his ISP could cut the entire connection until the problem is resolved. Seems like a good reason to care about the roommate's malware infested computer.
