Since the clients boot from the server, a virus at a client won't do any harm since it's gone with a reboot. ICT department here have done a good job :] . I've been told that they have tested the network with some dangerous network virii but the virii couldn't get to the main servers. That's why i'm not that frightened about a virus here (although i am also aware that no network is 100% safe and things can always go wrong).