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CyberSoc Write-Up foreigntransmission

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!

foreigntransmission

This OSINT challenge is from the section Signals Intelligence and is worth 400 points.

Task

Our signals intelligence team has captured a transmission originating from Western China and we have reason to believe that it may provide us with some kind of code that might be meant for a field operative of theirs. We’d like to know what it is.

The translation team is not available for us to utilise at the moment, so I’m wondering if you can use any of your digital tricks to work out what the code in the recording I’ve attached is?

The translation team is not available for us to utilise at the moment, so I’m wondering if you can use any of your digital tricks to work out what the code in the recording I’ve attached is?

Expected flag format: ###############

For completing this challenge, the audio file intercepted_signal.wav is provided as download.

Solution

After listening to the audio, we hear a female voice uttering a sentence in the Chinese language.

If we read the assignment with attention, we notice that it specifically talks about a signal picked up from West China. Through Wikipedia, we can find out that in the vast majority of western China is speaking the Mandarin language. Therefore, there is a good chance that the female voice in this audio file is speaking the Mandarin language.

cybersoc-foreigntransmittor-write-up-1

Because I do not speak nor understand the Chinese language, I have to find a way to convert the audio to text and then translate it into the English language. I found the website https://www.media.io/auto-subtitle-generator.html, which can translate audio to subtitles. This service has support for the Chinese (Simplified) language. After uploading the audio, the program is automatically adding the subtitles.

cybersoc-foreigntransmittor-write-up-2

After translating the subtitle into the English language, we can read what the female voice is saying: The access code is 415364214564383.

The flag: 415364214564383

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