Stegano on Anthrace | CTF Writeups

HackDay - Stegano

Wed, 30 Jul 2025 00:00:00 +0000

In this challenge, we are provided with a .wav file that, at first glance, appears to be a simple audio file. Our task is to analyze the file and uncover a hidden flag.

Step 1: Playing the Audio Link to heading

I started by playing the audio, expecting something unusual—perhaps some hidden message or distortion—but everything sounded normal. There was no apparent clue in the audio playback.

HackDay - Stegano & Forensic

Wed, 30 Jul 2025 00:00:00 +0000

Forensic Challenge - Hidden Flag Extraction Link to heading

In this challenge, we have a ZIP file containing a log file and two images.

Step 1: Log File Analysis Link to heading

I began by analyzing the log file and found five encoded words. I used dcode.fr to decode them:

ercbafr (ROT13) → reponse

c29sdXRpb24= (Base64) → solution

Huntress-CTF - DontBelieveEverythingOnTheInternet

Fri, 01 Nov 2024 00:00:00 +0000

Don't believe everything you see on the Internet! 
 
Anyway, have you heard this intro soundtrack from Half-Life 3?

The challenge starts by downloading an .mp3 file. While trying to process it in Python to extract metadata, I encountered errors. After several attempts, I started to wonder if it was actually an MP3 file—or something else. I wrote a function to determine the real file type:

import filetype

def check_file_type(filename): 
 kind = filetype.guess(filename) 
 if kind is None: 
 return "unknown file type." 
 return f"type: {kind.mime}, extension: {kind.extension}"

filename = 'src/Half-Life_3_OST.mp3' 
print(check_file_type(filename))

Thanks to this script, I found out that the file was actually a PNG: