Run a program that only allows whitelisted applications, and block all removable media. It's the only way you can be absolutely certain there is nothing running on your network that shouldn't be there. http://en.wikipedia.org/wiki/Whitelist#Application_whitelists

I think it's important to remember that the Unreal Engine has been free for educational use for a very long time. No doubt that there will be a similar number of restrictions on the CryEngine, mostly along the lines of not being able to reuse any code or assets for any future release. I imagine, however, that the unreal engine is probably a lot more useful to students as it is used in a much larger number of games or varying genres.