Capture the flag (cybersecurity)

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A team competing in the CTF competition at DEF CON 17

Capture the Flag (CTF) in computer security is an exercise in which participants attempt to find text strings, called "flags", which are secretly hidden in purposefully-vulnerable programs or websites. They can be used for both competitive or educational purposes. In two main variations of CTFs, participants either steal flags from other participants (attack/defense-style CTFs) or from organizers (jeopardy-style challenges). A mixed competition combines these two styles.[1] Competitions can include hiding flags in hardware devices, they can be both online or in-person, and can be advanced or entry-level. The game is inspired by the traditional outdoor sport of the same name.


Capture the Flag (CTF) is a cybersecurity competition that is used to test and develop computer security skills. It was first developed in 1996 at DEF CON, the largest cybersecurity conference in the United States which is hosted annually in Las Vegas, Nevada.[2] The conference hosts a weekend of cybersecurity competitions, including their flagship CTF.

Two popular CTF formats are jeopardy and attack-defense.[3] Both formats test participant’s knowledge in cybersecurity, but differ in objective. In the Jeopardy format, participating teams must complete as many challenges of varying point values from a various categories such as cryptography, web exploitation, and reverse engineering.[4] In the attack-defense format, competing teams must defend their vulnerable computer systems while attacking their opponent's systems.[3]

The exercise involves a diverse array of tasks, including exploitation and cracking passwords, but there is little evidence showing how these tasks translate into cybersecurity knowledge held by security experts. Recent research has shown that the Capture the Flag tasks mainly covered technical knowledge but lacked social topics like social engineering and awareness on cybersecurity. Therefore, researchers recommend that there should be a focus on non-technical topics as well in order to address cyber threats that are advanced.[5]

Educational applications[edit]

CTFs have been shown to be an effective way to improve cybersecurity education through gamification.[6] There are many examples of CTFs designed to teach cybersecurity skills to a wide variety of audiences, including PicoCTF, organized by the Carnegie Mellon CyLab, which is oriented towards high school students, and Arizona State University supported[7][8][9] Beyond educational CTF events and resources, CTFs has been shown to be a highly effective way to instill cybersecurity concepts in the classroom.[10][11] CTFs have been included in undergraduate computer science classes such as Introduction to Information Security at the National University of Singapore.[12] CTFs are also popular in military academies. They are often included as part of the curriculum for cybersecurity courses, with the NSA organized Cyber Exercise culminating in a CTF competition between the US service academies and military colleges.[13]


Many CTF organizers register their competition with the CTFtime platform. This allows the tracking of the position of teams over time and across competitions.[14] These competitions can be community, government or corporate. Since CTFtime began in 2011, there have been seven teams who have ranked as #1 in the worldwide position[original research?]. These include "Plaid Parliament of Pwning", "More Smoked Leet Chicken", "Dragon Sector", "dcua", "Eat, Sleep, Pwn, Repeat", "perfect blue" and "organizers". Overall the "Plaid Parliament of Pwning" and "Dragon Sector" have both placed first worldwide the most with three times each.[15]

Community competitions[edit]

Every year there are dozens of CTFs organized in a variety of formats. Many CTFs are associated with cybersecurity conferences such as DEF CON, HITCON, and BSides. The DEF CON CTF, an attack-defence CTF, is notable for being one of the oldest CTF competitions to exist, and has been variously referred to as the "World Series",[16] "Superbowl",[9][17] and "Olympics",[18] of hacking by media outlets. The NYU Tandon hosted Cybersecurity Awareness Worldwide (CSAW) CTF is one of the largest open-entry competitions for students learning cybersecurity from around the world.[4] In 2021, it hosted over 1200 teams during the qualification round.[19]

In addition to conference organized CTFs, many CTF clubs and teams organize CTF competitions.[20] Many CTF clubs and teams are associated with universities, such as the CMU associated Plaid Parliament of Pwning, which hosts PlaidCTF,[4] and the ASU associated Shellphish.[21]

Government-supported competitions[edit]

Governmentally supported CTF competitions include the DARPA Cyber Grand Challenge and ENISA European Cybersecurity Challenge. In 2023, the US Space Force-sponsored Hack-a-Sat CTF competition included, for the first time, a live orbital satellite for participants to exploit.[22]

Corporate-supported competitions[edit]

Corporations and other organizations sometimes use CTFs as a training or evaluation exercise.[citation needed] The benefits of CTFs are similar to those of using CTFs in an educational environment.[citation needed] In addition to internal CTF exercises, some corporations such as Google[23] and Tencent host publicly accessible CTF competitions.

In popular culture[edit]

See also[edit]


  1. ^ " / What is Capture The Flag?". Retrieved 2023-08-15.
  2. ^ Cowan, C.; Arnold, S.; Beattie, S.; Wright, C.; Viega, J. (April 2003). "Defcon Capture the Flag: Defending vulnerable code from intense attack". Proceedings DARPA Information Survivability Conference and Exposition. Vol. 1. pp. 120–129 vol.1. doi:10.1109/DISCEX.2003.1194878. ISBN 0-7695-1897-4. S2CID 18161204.
  3. ^ a b Says, Etuuxzgknx (2020-06-10). "Introduction To 'Capture The Flags' in CyberSecurity - MeuSec". Retrieved 2022-11-02.
  4. ^ a b c Chung, Kevin; Cohen, Julian (2014). "Learning Obstacles in the Capture The Flag Model". {{cite journal}}: Cite journal requires |journal= (help)
  5. ^ Švábenský, Valdemar; Čeleda, Pavel; Vykopal, Jan; Brišáková, Silvia (March 2021). "Cybersecurity knowledge and skills taught in capture the flag challenges". Computers & Security. 102: 102154. arXiv:2101.01421. doi:10.1016/j.cose.2020.102154.
  6. ^ Balon, Tyler; Baggili, Ibrahim (Abe) (2023-02-24). "Cybercompetitions: A survey of competitions, tools, and systems to support cybersecurity education". Education and Information Technologies. 28 (9): 11759–11791. doi:10.1007/s10639-022-11451-4. ISSN 1573-7608. PMC 9950699. PMID 36855694.
  7. ^ "ASU's cybersecurity dojo". ASU News. 2021-02-15. Retrieved 2023-07-18.
  8. ^ "picoCTF aims to close the cybersecurity talent gap". Retrieved 2023-07-18.
  9. ^ a b "Wanted: hackers. Reward: the best may get a spot at CMU". Pittsburgh Post-Gazette. Retrieved 2023-07-18.
  10. ^ McDaniel, Lucas; Talvi, Erik; Hay, Brian (January 2016). "Capture the Flag as Cyber Security Introduction". 2016 49th Hawaii International Conference on System Sciences (HICSS). pp. 5479–5486. doi:10.1109/HICSS.2016.677. ISBN 978-0-7695-5670-3. S2CID 35062822.
  11. ^ Leune, Kees; Petrilli, Salvatore J. (2017-09-27). "Using Capture-the-Flag to Enhance the Effectiveness of Cybersecurity Education". Proceedings of the 18th Annual Conference on Information Technology Education. SIGITE '17. New York, NY, USA: Association for Computing Machinery. pp. 47–52. doi:10.1145/3125659.3125686. ISBN 978-1-4503-5100-3. S2CID 46465063.
  12. ^ Vykopal, Jan; Švábenský, Valdemar; Chang, Ee-Chien (2020-02-26). "Benefits and Pitfalls of Using Capture the Flag Games in University Courses". Proceedings of the 51st ACM Technical Symposium on Computer Science Education. pp. 752–758. arXiv:2004.11556. doi:10.1145/3328778.3366893. ISBN 9781450367936. S2CID 211519195.
  13. ^ "National Security Agency/Central Security Service > Cybersecurity > NSA Cyber Exercise". Retrieved 2023-07-18.
  14. ^ "CTFtime". CTFtime. Retrieved 2023-08-18.
  15. ^ "CTFtime rankings". CTFtime Rankings. Retrieved 2023-08-18.
  16. ^ Producer, Sabrina Korber, CNBC (2013-11-08). "Cyberteams duke it out in the World Series of hacking". CNBC. Retrieved 2023-07-18.{{cite web}}: CS1 maint: multiple names: authors list (link)
  17. ^ Noone, Ryan (2022-08-15). "CMU Hacking Team Wins Super Bowl of Hacking for 6th Time - News - Carnegie Mellon University". Retrieved 2023-07-18.
  18. ^ Siddiqui, Zeba (2022-08-18). "Hacker tournament brings together world's best in Las Vegas". Reuters. Retrieved 2023-07-18.
  19. ^ "CSAW Capture the Flag". CSAW. Retrieved 2022-11-02.
  20. ^ Balon, Tyler; Baggili, Ibrahim (Abe) (2023-02-24). "Cybercompetitions: A survey of competitions, tools, and systems to support cybersecurity education". Education and Information Technologies. 28 (9): 11759–11791. doi:10.1007/s10639-022-11451-4. ISSN 1360-2357. PMC 9950699. PMID 36855694.
  21. ^ "These grad students want to make history by crushing the world's hackers". Yahoo Finance. 2016-08-04. Retrieved 2023-09-02.
  22. ^ Hardcastle, Jessica Lyons. "Moonlighter space-hacking satellite is in orbit". Retrieved 2023-07-18.
  23. ^
  24. ^ Woodward, Alan (2022-07-07). "'Some staff work behind armoured glass': a cybersecurity expert on The Undeclared War". The Guardian. ISSN 0261-3077. Retrieved 2023-07-18.
  25. ^ Qin ai de, re ai de (Drama, Romance, Sport), Zi Yang, Xian Li, Mingde Li, Shanghai GCOO Entertainment, 2019-07-09, retrieved 2023-08-15{{citation}}: CS1 maint: others (link)

External links[edit]

  • - an archive of historic, current, and future CTF competitions.