Firewalls and viruses

A firewall, properly set up, will prevent Trojans and other malware from getting into your PC via an open port, because it closes ports, and can even make your PC invisible (stealthed) to people trying to intrude. Some can also be set to scan e mail, though I let my AV software do that. It does not replace Antivirus software, but adds to it.

See ChrisRLG's informative page at

http://www.cjwd.demon.co.uk/compsafetyonline.html

If you want to check whether some Trojans could get in, run the on line check at

http://www.anti-trojan.net/en/onlinecheck.aspx 

or try the various checks here:

http://scan.sygate.com/