Do The Loop — DownUnderCTF 2021

CTF EVENT : DownUnderCTF 2021

DIFFICULTY: Easy

CATEGORY: FORENSICS

POINTS: 100

CHALLENGE:

Do the loop doop doop…

Flag format: The STRING you end up with after solving challenge, case insensitive. File to download

Download file: monorail.wav

When we listen to the audio, we can hear a morse code in the background. The flag should be hidden in this morse code.

We can use Audacity to investigate the “waves”.

When opening the .wav file with Audacity, you should change the view. Set is as Spectrogram. It will allow you to better see the morse code.

Now you can see the morse code.

From here you can write down the code (I did it manually). Every long line means “-“, every sort line means “.”, and a big space means just space.

Your morse code will look like something like this:

The whole morse code is:

.. -.-. --- ..- .-.. -.. .-.. .. ... - . -. - --- - .... .. ... --- -. .-.. --- --- .--. .- .-.. .-.. -.. .- -.--

You can use this website in order to decrypt it: https://morsecode.world/international/translator.html

You find this: ICOULDLISTENTOTHISONLOOPALLDAY (I COULD LISTEN TO THIS ON LOOP ALL DAY)

The challenge says that challenge is case insensitive, so the final flag is

Flag : icouldlistentothisonloopallday

CONCLUSION:

It was my first time playing with morse code. It was fun but in my opinion, I don’t think that this challenge is a Forensic challenge.

I hope that my writeup helped you to understand better all the aspects of this CTF. If you want to read more writeups like this one or have any questions, you can find me on Twitter @dropn0w.

Stay safe and keep learning!

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