Capture the Flag

The goal of the capture the flag (CTF) is to solve some simple problems related to the material you've studied so far. The challenges range from finding hidden messages, to encrypting and decrypting messages, and analyzing webpages and executables.

By continuing, you agree to not to do any harm with this information or other similar information on the internet.

The course consists of 1 part.

Before starting the course

Please read the instructions on how to start and pass the course. Especially, pay extra attention on 'how to pass' section as this course requires additional steps in order to receive ECTS credits.

Completing the course requires setting up TestMyCode environment. Please read the installation instructions.

Support channel and contact information

For support channel use Discord (use #csb_general channel).

For any further questions, contact grp-cybersecuritybase(at)removethis.helsinki.fi.

How to pass the course

The challenges in this CTF come in three difficulty levels: easy, medium and hard.

In order to ensure everyone has a fair chance to get the first completion, we're releasing the challenges in batches — easy challenges are to be released on Wednesday (13.3.2024), medium challenges on Thursday (14.3.2024), and hard challenges on Friday (15.3.2024).

The exercises are published starting from 14:00, and new exercise will be added roughly every 20 minutes.

There are 10 easy challenges, 10 medium, and 3 hard.

The exercises can be found here. Use your MOOC account to login.

To finish a challenge, find a special code and submit it to the site.

For certain challenges, binary inspection command line tools like strings or xxd will be useful. Passwords will be often encoded and/or hashed and/or encrypted. Part of the challenge is to figure out which encoding is being used, online converters may prove useful.

Some of the challenges expect you to analyze and/or execute a Linux 64-bit binary. If you have an incompatible OS consider setting up one in a VirtualBox.

To pass the CTF, you need to complete at least 8 easy challenges and at least 7 medium challenges, before the deadline. There is no need to complete hard challenges to pass the course. The number of students that have completed a challenge before you has no effect on passing the course. The deadline for completing the challenges is 30.4.2024.

Medium challenges are open after you complete 80% of easy challenges. Hard challenges are open after you complete 80% of medium challenges.

This competition is individual work. Please do not share your solution or spoil the exercise, let's keep the competition fair and fun for everyone! :)