In the 1990s, Microsoft had a problem: Windows seemed to suffer from endless security problems that hackers and other online villains were quick to exploit. One way to fight back was to install a firewall - an app that blocked malicious and/or unwanted network traffic and that could ensure that dodgy software couldn't sneak onto your PC.
Microsoft began building its own firewall into Windows and that's still the case today, but attacks still happen and additional software can make your system even more secure. These are the firewall apps we think you should consider using no matter which version of Windows you're running.
If we've missed your favorite free firewall - whether it's a standalone program or built into a full online security suite - let us know in the comments below.