OK, no control. What can you use instead? (Score 1)

One of the most powerful things in that kind of environment is peer pressure. Make it very clear via email what the problem is and what is causing it. When there is a problem, run some port scanners and identify the problems and the users that are causing the problems. Let the problems persist and send a mass email identifying the users and the nature of the problem along with the fix (yes the email to all will be slow due to the probs but that's part of the strategy). Peer pressure will do the rest.