TCPBlock is described as 'Lightweight and fast outbound firewall for Mac OS X 10.5 or later developed by delantis.com. Very simply to set up and use. And best of all it doesn't nag' and is a Firewall in the security & privacy category. There are seven alternatives to TCPBlock for a variety of platforms, including Mac, Windows, Linux, VirtualBox and Self-Hosted apps. The best TCPBlock alternative is Little Snitch. It's not free, so if you're looking for a free alternative, you could try TinyWall or Gufw. Other great apps like TCPBlock are CacheGuard Gateway, Radio Silence, TripMode and Flying Buttress.