Beginner capture-the-flag · Learn by doing

Start small.
Think like a defender.

A guided introduction to CTF puzzles, with a short lesson before every challenge so you always know what to try next.

Begin the walkthrough

01 / The approach

Learn the move.
Then make it.

A beginner capture-the-flag with step-by-step walkthroughs that teach each technique before you try it yourself.

Read the lesson, follow the example, and submit the flag when you are ready. These are safe, local exercises designed to make the first steps feel approachable.

View the challenges

02 / The learning path

Three techniques
to try today.

Read the writeup.
Then find the flag.

01WEB EXPLORATION

Look closer

Web pages contain more than what appears on screen.

Step-by-step writeup
  1. Right-click the page and choose View Page Source, or press Ctrl + U.
  2. Use Ctrl + F to search for flag.
  3. Look through comments and linked text files too. Comments are invisible in the rendered page, but visible in the source. Open the plain-text hint.
  4. Submit the value that starts with WVSU{.

Tip: developers leave comments for themselves, and sometimes a flag is hiding there too.

02LINUX BASICS

Use the shell

Basic commands can turn an unfamiliar folder into a map.

Step-by-step writeup
  1. pwd prints your current folder so you know where you are.
  2. ls lists the files in that folder. Look for a filename that deserves a closer look.
  3. cat notes.txt prints a text file directly in the terminal.
  4. Read the note, then submit the flag it reveals.

Tip: command-line tools are small, composable, and excellent at revealing plain-text clues.

student@cic-lab:~$ practice-shell
Type help to see available commands.

03CRYPTO BASICS

Decode the clue

Encoding is not encryption, and a decoder can prove the difference.

Step-by-step writeup
  1. Base64 often uses letters, numbers, +, /, and ending = padding.
  2. Copy the string into a Base64 decoder, or use echo '...' | base64 -d on Linux.
  3. Read the decoded phrase. It gives you a short Caesar cipher to finish.
  4. Shift each letter three places backward to reveal the flag.

Tip: Base64 changes how data is represented; it does not make the data secret.

RECOVERED STRING Q0FFU0FSOiBaWVZYe3drdWhoX3Z3aHNfZ2hmcmdodX0= Base64 first · then follow the message

03 / Keep exploring

Your first flag
is only the start.

Check in later for new challenges, new techniques, and new ways to practice thinking like a defender.

Want more? Check out picoCTF