Capture the Flag (CTF) in computer security is an exercise in which “flags” are secretly hidden in purposefully-vulnerable programs or websites. Competitors steal flags either from other competitors (attack/defense-style CTFs) or from the organizers (jeopardy-style challenges).Several variations exist, including hiding flags in hardware devices. Competitions exist both online and in-person, and can be advanced or entry-level. The game is based on the traditional outdoor sport of the same name. Flags are often stylised with a combination of letters and numbers such as ICECLUE{[email protected]_lik3This}.