tmpfs.tech · all tracks · Firewall (nftables)

Author a base nftables ruleset

Firewall (nftables) · easy · live throwaway Linux box · 3 tiered hints

There is no firewall engine here — write a correct nftables ruleset to /etc/nftables.conf: a table 'inet filter', an 'input' chain (type filter hook input) with policy drop, and a rule that accepts tcp dport 22.

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How it works

Press start and you get your own real, disposable Linux VM — in the browser terminal or over SSH. Work the task on a live system; tmpfs.tech grades your solution automatically against the actual machine state, then throws the box away. No install, free to try as a guest.

More Firewall (nftables) challenges

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

• Accept Related ICMP Errorseasy · in-browser
• Always trust loopbackeasy
• 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
• Output chain accepteasy · in-browser

See all Firewall (nftables) challenges →

FAQ

Is it free? Yes — play as a guest, no signup required to start.

Do I need to install anything? No. Everything runs in your browser, or connect over SSH if you prefer your own terminal.

How is it graded? Automatically and deterministically — your work is checked against the real state of the machine you worked on.