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Match OS by Passive Fingerprint

Firewall (nftables) · pro · solved in-browser (no VM needed) · 3 tiered hints

Write /etc/nftables.conf with a table inet filter and an input chain (type filter hook input, policy drop). Use the passive OS fingerprinting expression to drop packets that look like Windows: match `tcp dport 22` and `osf name "Windows"`, log with prefix "win-ssh ", and drop. (Authored config, graded structurally — the engine isn't run here.)

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FAQ

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