How I write CTF walkthroughs

A useful CTF walkthrough is not a command history with the mistakes deleted. It is a reconstruction of the reasoning that moved the challenge forward.

The final exploit matters, but the observations around it are usually what transfer to the next box.

Start with scope

Only test systems you own or have explicit permission to assess. For CTFs, keep the challenge name, platform, category, and rules with the notes. That context prevents a technique from being mistaken for permission to use it elsewhere.

Keep three streams of notes

I separate the work into three rough streams while solving:

1. Observations — facts the target revealed: ports, headers, versions, file types, error messages.
2. Hypotheses — what those facts might mean and how I could test them.
3. Actions — commands, requests, payloads, and results.

This makes it easier to see where I made a leap. If a walkthrough jumps from an open port to a working exploit, the missing material is usually in the hypothesis stream.

Preserve the dead ends that teach

Not every failed attempt deserves space. Keep the ones that expose a common assumption or reveal something new.

For each useful dead end, write one sentence answering: why was this reasonable, and what ruled it out? That is enough to teach without turning the article into a transcript.

Explain before showing the command

A command block should confirm an idea already introduced in the text. Before the command, state what you are testing. After it, point to the part of the output that changed your next move.

# Example only: enumerate services on a CTF target you are authorized to test
nmap -sV -sC 10.10.10.10

The tool is not the insight. The useful part is why that scan was appropriate and which result deserved attention.

Redact without breaking the lesson

Remove live credentials, reusable tokens, private IPs outside the lab, and anything the challenge rules prohibit sharing. Replace secrets consistently so readers can still follow the relationship between steps.

End with the chain

I finish with a compact chain of evidence:

Observation → hypothesis → test → result → next observation

If I cannot summarize the solve that way, the walkthrough probably still contains a hidden jump. Fixing that jump is where the writing becomes useful.

The goal is not to prove the challenge was solved. The flag already does that. The goal is to leave a map that makes the next investigation better.