Firewall.

Firewall is what allows or blocks programs from connecting to the internet. Network firewalls are a software appliance running on general purpose hardware that filter traffic between 2 or more networks.

"Hardware firewalls" are also found in most network routers and can be configured and setup through the router setup.

"Software firewalls" are designed to protect the computer they are installed onto by blocking any unrestricted programs from sending and receiving information from the network or Internet. A good example of a software Firewall is the Windows Firewall that is included with Microsoft Windows.