tmpfs.tech · all tracks · Firewall (nftables)

Restrict SSH to a CIDR

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

Write /etc/nftables.conf (base table inet filter, input hook, policy drop) accepting tcp dport 22 ONLY from 10.0.0.0/8. (Authored config, graded structurally — the engine isn't run here.)

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How it works

Open the challenge and an in-page editor appears — write your answer and tmpfs.tech grades it server-side against the same checks a real box would run. No VM, no install, no signup needed to try.

More Firewall (nftables) challenges

Author and reason about nftables rulesets — filtering, NAT and policy.

• Accept Related ICMP Errorseasy · in-browser
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• Author a base nftables ruleseteasy
• Define a Variable for WAN Interfaceeasy · in-browser
• Drop Invalid Conntrack Earlyeasy · in-browser
• Idempotent ruleset headereasy · in-browser
• Include a Drop-In Ruleset Fileeasy · in-browser
• Named hook priorityeasy · in-browser

See all Firewall (nftables) challenges →

FAQ

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Do I need to install anything? No. Everything runs in your browser.

How is it graded? Automatically and deterministically — your work is checked against the exact rules the live box would apply.