People have already mentioned that you can monitor traffic. But besides that, it should be noted that neither of these are necessarily cheating - they can be used to disrupt games but that is not the same thing. Crashing servers is just being annoying/trolling, and same with fake chat (which is easier to notice, anyway). The only chat related thing that I can think of which would be cheating is spying on the other team's teamchat, but that too could be noticed with a good eye.