I have the ability to block URLs
I can block URL keywords like proxy (blocks myproxy.com, but also proxyz.com [potential for unintended consequences])
My new strategy is that I can have certain words/combinations listed on a page trigger a block (PHPproxy or CGIproxy listed on the page = block)
Can't do that with filter or tunnel though, too many false positives ... but I am hoping the people who run these sites like to brag or at least mention which type they use.
below are some of the latest, only had one known student visit 1 site (turned in a faculty member) but all these were unblocked as of today.