Perhaps you've heard of a firewall. If you're an architect, you might be thinking of the actual fire-proof walls used to stop the spread of blaze from, say, apartment to apartment. If you're pretty much anyone else, a firewall is one of the many network settings you may have tinkered with when configuring your Internet. A computer firewall is a network security system that controls incoming and outgoing traffic, creating a barrier between your internal network and the flaming, virus-filled Internet.
Firewalls have been common since the 90's. Which is why it might be surprising to learn that an "inventor" patented firewalls in 2000. Though he let his patent expire, it has recently been picked up by a patent troll, who is using it sue pretty much everyone who sells products related to network security.