Firewalls act as a gatekeeper between your PC and the Internet. The built-in Windows firewall only works on incoming connections, whereas most malware use outgoing connections as well.

To protect against those, we recommend a third party firewall. Either of these firewalls requires a "learning curve" in order to get to know which programs on your PC are safe. For the first couple weeks, expect to get numerous pop-ups from the firewall asking whether you recognize programs that are trying to connect to the internet. As the firewall learns, the warnings will become less frequent.

Firewalls

Comodo - Best overall, but lots of pop-ups during learning phase

Zone Alarm - A bit less demanding and more user-friendly