Opposable Thumbs - H@cktivityCon CTF

Category: Forensics
Solves (at time of writing): 418
Description: The flag is right between your finger tips.

Opposable Thumbs

We are given a thumbscache_256.db file.

From my days of using Windows I remember there being a thumbs.db file to store thumbnails of images or icons in a folder.

After googling around for a bit I found this Thumbcache Viewer.

I downloaded it, was in EXE format but thanks to wine I could open it anyways.

After opening the file with a tool we'll be greeted with this screen:

We can see a bunch of information here, clicking on one of the entries showed the corresponding image.

I went through all of them but didnt find anything interesting.

Then I noticed the "Data Checksum" column.

For some of them its just 0, but some have an actual checksum.

Looking through the files with an actual checksum, only one of them seemed invisible.

Thinking that's the flag I extracted it by right-clicking the entry and clicking save as.

After saving it we can open it in an image viewer aaand:

~sw1tchbl4d3, 31/07/2020 (dd/mm/yyyy)