The best thing that happened during my time at ITU was joining ITU Underground. It started with the freshman CTF, where I later submitted my first challenge, Hal-F20, to ctf.itunderground.dk. The following semester I joined the board, and together we set out to organize something much bigger.

On 11th April 2025 we teamed up with Scrollbar to host our first major CTF event. Participants could earn free drinks by solving cybersecurity challenges. Top teams also won limited-edition shirts, which the organizers wore during the tournament. The idea was inspired by our proffesor Thore Husfeldts long-running event Will Code For Drinks in which participants solved competitive programming challanges for a chance to win a free drink. Since then we have organized 3 big hacking events (2 hack for drinks and 1 hack for snacks) Over the next year I helped organize three events in total: two Hack for Drinks and one Hack for Snacks. As the community grew, our second Hack for Drinks attracted more than 100 participants.

I created the visual identity for the event, including a reusable design system that future organizers could build on by swapping graphics and color palettes while keeping a consistent style. This resulted in digital advertisment, posters, stickers, and merch. I designed posters, stickers, shirts, social media graphics, and event branding used across all three events.

(posters through the years)

The challenges

Alongside design, I authored challenges ranging from beginner friendly forensics, reversing, and game hacking to more advanced reverse engineering and web exploitation. I love making challanges and the biggest inspiration for challange ideas I get from hands-on hacking, and then wanting to show off a cool vulnerability without breaching any non-disclosures.

One of the featured challenges was a prompt injection task built around an open source Facebook LLM. Contestants interacted with a fake CV scanning HR assistant and had to recover four hidden flags by combining prompt injection techniques such as role attacks and glitch tokens.

Try our challanges on ITUndergrounds official CTF site!

Another challenge was a small Godot platformer starring the WHFD mascot. Players had to bypass the game’s win condition by patching the executable through memory inspection. The game-hacking challenge was a small platformer I built in Godot, starring the little WHFD pixel guy. Players collected virtual hats but needed 99,999 points to win despite only 8 caps existing on the map. Intended solve: overwrite your score and get the flag.

Challanges im especially proud of:

Super

A web challenge centered around a university exam portal. Players explored the application, uncovered weaknesses in the account system, and ultimately escalated their privileges to gain access reserved for a super administrator. The challenge combined multiple realistic vulnerabilities into a single attack chain inspired by common mistakes seen in production applications.

https://super.hfs.itunderground.dk/

Sealed

A Python sandbox escape inspired by the Python jail challenges from Max’s CTFs in 2025. I designed it to be slightly more challenging while making it easier to interact with through a dedicated web interface. Contestants had to escape a heavily restricted eval environment without access to Python’s built-in functions or several commonly abused keywords, rewarding a deep understanding of Python internals rather than brute force.

https://sealed.hfs.itunderground.dk/

Prison Realm

A reverse engineering challenge built around a custom multi-layer Python obfuscator. Rather than simply deobfuscating the provided program, players had to understand the transformation itself and use that knowledge to generate a valid solution. The challenge focused on automation, pattern recognition, and reversing an unfamiliar encoding scheme instead of manually peeling back layers.

https://ctf.itunderground.dk/challenges#Prison%20realm-99

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Numbers

The first Hack for Drinks welcomed over 60 participants across 29 teams. By the second event, attendance had grown to more than 100 participants, establishing Hack for Drinks as one of the club’s largest recurring events.

Closing

The events continue to run today, and I’m proud to have helped shape both their visual identity and many of the challenges that introduced new members to competitive hacking.A huge shoutout to the rest of the organizers in the hacking club. There’s no way we could have pulled off events like these without such an amazing group of people. I plan to keep supporting these events however I can! Just from the outside this time. :D