NahamCon2021 CTF - Pollex - Writeup
Introduction Today we're doing a CTF writeup for the Pollex challenge from the NahamCon2021 CTF. Pollex is a steganography challenge and after we started the challenge we downloaded the associated file we checked what kind of file it was: file pollex This looks like a regular jpg file. Let's check its exif info with Exiftool : The output from the Exiftool tells us that there's an embedded thumbnail in the file, also the thumbnail is embedded as binary data. We can extract embedded binary thumbnail data from images using Exiftool by supplying the following command: exiftool -b -a -preview:all -W /home/kali/walks/ctf/nahamcon2021/%f_%t%-c.%s pollex The file that was created is named pollex_ThumbnailImage.jpg. Let's view it now: xdg-open pollex_ThumbnailImage.jpg Summary After downloading the file, we used Exiftool to analyze it, discovering that there was a thumbnail embedded in the image. Using Exiftool, we extracted the thumbnail and viewed it, revealed our ob...