The first line of defense is a trustworthy provider... read more.

As a second line of defense my home-network is protected by a trustworthy hardware firewall inside the router. Wireless is fine if you accept only the IP addresses of known computers. Configure the router decently or you have an open gate in stead of a line of defense.

Third line of defense:
A trustworthy antivirus

And a software firewall:
Nondisputandum uses at the moment:

Comodo (5/5)
This fully functional and free firewall is for slightly more advanced users. It protects itselves agains shut-down by malwarez, trojans & stuff. It takes some time to get used to you, but once trained, it serves you like an invisible guardian angel. Downside : You have to take their anti-virus with it. Though it might be a fair choice to do so.

Zonelabs (4,5/5)
Free software for inexperienced and experienced users. Zone Alarm is a good alternative for those who want to use this firewall in combination with a separate antivirus solution. Zonelabs also offers a payware suite with antivirus detection. They ccasionally ask if you want to be informed about their Pro (payware) version.

Sygate Personal Firewall
Free standard version. (4,5/5)
 

You indisputably NEED it!

If not an active hardware wall in your router than software on your pc. Or better, use both. If one has a flaw, and they have... the other will protect. I strongly advice not to use 2 software walls on one computer. That is asking for trouble.

Do not fully trust the Windows XP second edition firewall. It only blocks incoming traffic (Microsoft) and leaves outgoing traffic open.

Of cource,... almost every security company offers a firewall in their payware suite. You can trust companies like Pandasoftware and ZoneLabs. Be cautious with Norton. Very good software but IMHO you can use your remaining resources better...

 

Audit My PC (5/5)
Check if your firewall security needs more fine tuning.

Firewall Leak (4/5)
Choose between 15 tests.

Norton Security Scan (5/5)
Check if your computer is secured against Hackers, Windows Vulnerabilities and Trojan Horses.

Shield Up (4/5)
GRC.com Checks your internet connection security: port scanning and netBIOS implementation.

Sygate Firewall Scan (5/5)
A rapid test from the makers of Pest Patrol & Sygate Firewall. It should not find what services you are running, neither your computer name. Else, check your firewall settings.