I recently ended up in a bit of a pickle due to a user of my image board posting a lot of cp without me noticing because both me and the other mod were not able to check the boards for a few weeks (good idea, that). My host semi-demanded that I disallow anonymous posting, or that I keep a much closer watch on my boards. Reasonably enough they have limited patience with these sort of issues.

My question, however, is how can we as administrators hinder this in a simpler way than keeping a close eye on our boards 24/7?
I found that the user posting this content (among others) used a proxy connection to connect to the website. Is it possible in any way to hinder proxy connections to a server, for instance?