Obscurity was a medium Linux box that offered completely custom written software. This was a cool concept to explore, because it required diving into source code to spot vulnerabilities. For the foothold, this was fuzzing to find the source of the web server and then spotting a vulnerable exec function based on user input. User required a bit of reverse engineering to decrypt a key used in a custom encryption tool. Finally, root access came from abusing the temporary write of password hashes during login attempts for a custom SSH service.