Our pick for the best firewall software is a no brainer. Zone Alarm is the industry leader in personal PC firewall protection. The free version of ZoneAlarm provides solid security for your internet connections. It is great at blocking hackers, spyware, and trojans from entering your computer via the web. It provides custom security controls which will allow you to make your PC invisible to hackers.
There are also more advanced versions of Zone Alarm which are available from $19.95 to $69.95 depending on the features you are looking for. Their top of the line product offers anti-spyware, anti-virus, anti-phishing, spam blocking, parental controls, and identity theft protection. Not a bad package for just $69.95.