This repository aims to be an archive of information, tools, and references regarding CTF competitions. CTFs, especially for beginners, can be very daunting and almost impossible to approach. With some general overviews of common CTF subjects and more in-depth research and explanation in specific topics both beginners and veterans can learn, contribute, and collaborate to expand their knowledge. What is a CTF? CTFs are computer security/hacking competitions which generally consist of participants breaking, investigating, reverse engineering and doing anything they can to reach the end goal, a 'flag' which is usually found as a string of text. DEF CON hosts what is the most widely known and first major CTF, occurring annually at the hacking conference in Las Vegas. Many different competitions have branched off since then, and numerous ones are available year-round. One of the best places to see when CTFs are being scheduled is ctftime, an active website with calendars and team rankings. Example: A very simple type of CTF challenge consists of looking at the source code of websites or programs to find flags and/or hints.