Firewalls are a vital part of network security, so it’s important for a sysadmin to be familiar with how they work. If you understand firewalls, you can keep your network secure by making intelligent choices about the traffic you allow in and out.
Because "firewall" is such an exciting name, people often imagine an intricate Tron-style neon battle happening on the outskirts of a network, with packets of rogue data being set alight to protect your users’ the techno fortress. In reality, a firewall is just a piece of software controlling incoming and outgoing network traffic.
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