@krishnachaytanya: Firewall, explained. Every port on your server is a door. With no rules, every one of them answers. A port scanner knocks on all of them until something replies, and that reply is how an attacker maps your machine. A firewall checks each door number against your rules. ALLOW 443, ALLOW 80, deny the rest. Port 3306, your database, should never have been reachable in the first place. The part people miss: a blocked packet is dropped, not refused. No reply at all. The scanner hears silence, so it cannot even tell the door is there. That is the difference between DROP and REJECT, and it is why a scan of a firewalled box comes back empty instead of coming back closed. One honest limit. A firewall reads the address on the packet, never the contents. Anything addressed to an open port walks straight in. That is what a WAF is for. #trending #systemdesign #cybersecurity #devops

KrishnaChaitanya|SystemDesign

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Wednesday 14 October 2026 13:00:57 GMT