Fortunately, we have security measures like firewalls, which prevent bad actors from gaining unwanted access to networks. Preventing your internet from crashing isn't the only positive you can gain from a network firewall. There are also customizable uses for firewalls, like blocking inappropriate online content from your children. Here's what you need to know about firewalls, including how they work and why they're important. Firewalls, explained A firewall is like a bouncer for your internet activity, creating a security barrier between your home network and unwanted intrusion from the internet at large. Firewalls can be cloud-based, or they can be a physical piece of hardware that you buy and connect to your modem and router. (For the most part though, modems and routers will come with pre-implemented firewall technology.)