What is a firewall?
A firewall sits between your server and the outside world. It decides which network traffic is allowed to reach your machine and which should be dropped. Think of it as a bouncer at a club: only people on the guest list get in.
UFW, short for Uncomplicated Firewall, is Ubuntu’s front‑end to iptables. It lets you write rules with simple commands instead of juggling raw tables.
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