I too studied about the behavior of trojans and all. But i think u re not so familiar with that. Whenever a file needs to access internet, A good AV like kasersky will ask the user that " this process tries to connect with the internet and asks for the option "Allow or Block". So u can very well decide whether to allow it or not. Jus download any trojans and check that with a good antivirus with up to date database.