CyberSoc Write-Up thermalentry

About CyberSoc

The Cyber Investigator CTF was created by Jack Tilson of Cyber Society at Cardiff University. There are over 30 free & predominantly OSINT-based challenges drawing from a range of scenarios, putting your analytical skills to the test!


This OSINT challenge is from the section Covert Operations and is worth 500 points.


One of our undercover officers has been following a suspected financial crime kingpin and they keep visiting a lockup in a secluded area of London - we have no idea what is in there.

A couple of nights ago, the officer noticed that there is a digital PIN pad used to open the lockup door, and shortly after the suspect entered and closed the door behind them, our officer promtly approached the PIN pad and took a photograph of the keys with a thermal camera.

Research into the PIN pad reveals that it only accepts four digit codes, so that should make things easier.

What is the PIN code for the lockup? It will be much easier for us to make a subdued entry to find out what is in there without compromising our investigation through forcing our way in.

Note: You only have 5 attempts so inspect the image very carefully before checking your answer.

Expected flag format: ####


This challenge was a nice and easy one. Let’s start with the solution.

In the image, we see a picture taken from a thermal camera. The suspect has entered a code on the Numpad. We have to figure out the PIN combination.

The number the suspect is pressing will glow. As soon the suspect is pressing another number, the heat signature starts fading away as time goes by, and the newly pressed key will start to glow. In this way, a pattern is visible through a thermal camera. We know that this is a 4-digit PIN.

To solve this challenge, we have to follow the pattern, starting with the key with the lowest temperature and ending at the key with the highest temperature. If we follow this pattern, we end up with the following PIN: 4185

The flag: 4185

This post is licensed under CC BY 4.0 by the author.