Time for a stego writeup..
Can you hear it? Sounds like a flag… Note: The flag only contains lowercase characters.
$ mediainfo stegosaurus.mp3
Complete name : stegosaurus.mp3
Format : MPEG Audio
File size : 2.78 MiB
Duration : 3mn 2s
Overall bit rate mode : Constant
Overall bit rate : 128 Kbps
Track name : The Sub Human Spectrum Song
Performer : The Mentor
The audio is a 3 min recital of The Conscience of a Hacker (aka The Hacker’s Manifesto).
The first minute of audio appears to contain some odd low-frequency ‘pops’, so let’s open the file up in Audacity to investigate:
For those unfamiliar with Audacity: you can press the arrow next to the track name to switch from waveform (top) to logarithmic spectrogram (bottom).
Something appears to be going on there up until the ~1m10 mark. Let’s enhance (err.. zoom):
Looks like someone has hidden some Morse code in there. As all the morse data appears to be below 100 Hz, we can use a low pass filter (effects menu, cutoff 100 Hz) to ease transcription:
That’s better. Now transcribe and decode it using your favorite morse decoder (I used Android Morse keyboard) to get the flag: