Getting Started with CTFs

A CTF (Capture the Flag) is a security competition where you solve challenges to find a hidden string called a flag. Flags are usually formatted like flag{some_text_here}.

They are the best way to apply what you have learned in a structured, consequence-free environment.

Formats

Jeopardy-style: A set of challenges across different categories. Solve a challenge, get a flag, earn points. You pick what to work on. Most beginner CTFs use this format.

Attack/Defend: Two or more teams each run identical vulnerable systems. You attack the other teams’ services while defending your own. CCDC uses this format.

Start with jeopardy. Attack/defend comes later.

Where to Start

Start on PicoCTF or TryHackMe. Do not skip to HackTheBox and wonder why it is hard.

How to Approach a Challenge

1. Read the description carefully. The intended vulnerability is usually hinted at.
2. Enumerate. What do you have? A file? A web service? A binary? Network access?
3. Identify the category. Is this web? Crypto? Forensics? (See Categories.)
4. Try the obvious thing first. Beginners often over-think. Check the simple cases.
5. Search. Look up the technology, the error message, the behavior. CTF knowledge is cumulative.
6. Ask for a nudge, not an answer. Getting pointed in the right direction is fine. Getting the solution handed to you teaches you nothing.

Writing Writeups

After you solve a challenge, write it down. Even a rough Markdown file with what you tried and what worked.

• It solidifies your understanding.
• It helps your teammates who got stuck.
• It becomes a reference when you see the same technique again.

Good writeups explain why something worked, not just what commands you ran.

Tools You Will Reach For

These are not category-specific — they come up everywhere:

• CyberChef — decode, encode, transform data with a GUI. Try it.
• strings — extract printable strings from a binary file
• file — identify what type of file something is
• xxd / hexdump — view raw bytes of a file
• Burp Suite — intercept and modify HTTP traffic

Using AI in CTFs

AI is a legitimate tool in CTF work. Knowing how to use it well is a skill in itself.

Where it genuinely helps:

• Identifying encodings: Paste an unknown string. “What encoding is this and how do I decode it?” AI recognizes base64, hex, rot13, URL encoding, JWT, and many others instantly.
• Explaining vulnerability classes: “What is a padding oracle attack and how does it work against AES-CBC?” Better than reading a dry Wikipedia article.
• Scripting: Tell it the protocol, the port, and what the service responds with. Ask for a Python socket script to interact with it. Use that as the starting frame.
• Stuck on a hint: Paste the challenge description and say “I’ve tried X and Y, what categories or techniques should I look into?” It will not give you the flag — it will point you in a direction.
• Reading assembly: Paste a short disassembled function and ask what it does. Speeds up reverse engineering significantly.
• CyberChef recipes: Describe the transformation you need. AI will write the CyberChef recipe.

Where it fails in CTFs:

• Custom or novel challenges: AI has not seen them and will hallucinate solutions.
• Specific offsets, addresses, or binary internals: it cannot run the binary.
• The actual solve: it can outline an approach, but you have to execute it.

Use AI to accelerate learning and eliminate grunt work — not to skip the thinking.

References

• PicoCTF
• CTFtime.org
• CTF101 — beginner field guide
• LiveOverflow YouTube — CTF writeup videos