If you use an external firewall (linksys), do you still need to install anti-spy,virus software?

Yes. The hardware firewall will protect from outside attacks, like if someone is trying to connect to unsecured ports on your computer to take control of it. However viruses and spyware come as programs you specifically download. They might be hidden inside of another program such as a game or a file sharing application. Kazza was a file sharing program that was known to have spyware.

Because it is something you are actually downloading to your computer and not an outside attacker trying to send you something, you need software (anti-virus/spyware) to scan those files.

Also, even with a hardware firewall, I would recommend a software one like ZoneAlarm just as a backup. AVG is a good antivirus program and Spybot S%26D is an excellent anti-spyware program. I've provided links to these three applications below.

If you use an external firewall (linksys), do you still need to install anti-spy,virus software?symatec

A firewall is to prevent direct attacks from the internet and other computers.

An Anti-Virus detects and blocks virul attacks in Emails downloads, ect. They do not do the same job so yes you need an anti-virus program. I recomend one called AVG you can download from free.grisoft.com and it is free for the anti-virus portion. I also recomend installing spy-bot search and destroy (from www.download.com) for malware protection (spyware and adrare). I recomend this over most of the comercial anti-virus software as it is "FREE" accurate and does not slow your computer like the commercial options.