Backdoor – Security CTF Platform

In plain words

Backdoor is a security capture-the-flag platform where users solve cybersecurity challenges and puzzles. Designed for people interested in learning and practicing information security skills, it offers a competitive environment to test hacking knowledge across various difficulty levels. The platform enables participants to compete against others while discovering vulnerabilities and security concepts through hands-on problem-solving.

written from the facts on this page · September 2026

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  A proof-of-concept FoundationDB based network block device backend2018 · github.com · ▲192

  A totally proof-of-concept FoundationDB based network block device backend - dividuum/fdb-nbd

• HC
  Hackchain – Continuous Bitcoin-Inspired CTF Competition2016 · hackcha.in · ▲83
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  BunkerWeb – The Open-Source Web Application Firewall (WAF)2024 · github.com · ▲120

  🛡️ Open-source and cloud-native Web Application Firewall (WAF) - bunkerity/bunkerweb

• HA
  HackerSurf – All the hacker jobs in one place2014 · hacker.surf · ▲106
• 
  CryptoHack2020 · cryptohack.org · ▲81

  A fun platform for learning cryptography

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  CSEM CTF2025 · csem.sturtles.in · ▲11

  Cyber Security Learning Make Easy

• 
  SimCity, but with Permits▲909

  A free city-building game in your browser. You are the mayor. You know what the city needs. Now get it past the zoning board, the neighbors, the appeals court and the next election.

  Life & fun · 1d ago · permit.petercai.com

• IV
  I've been paying for a rural Tanzanian's education for 10 years▲778

  Life & fun · 14d ago · tanzaniaeducationproject.org

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  Bigwords.page – Turn any screen into a sign. The URL is the app▲728

  Turn a phone, tablet or TV into a sign. Type a message and it fills the screen: welcome signs, timers, Wi-Fi passwords and more. No app, no account, free.

  Life & fun · 15d ago · bigwords.page

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  Guitoro, a virtual guitar you strum with your keyboard▲573

  Play a free virtual guitar online with your keyboard or by touch. Slow songs down and see every chord, string and strum. Acoustic, classic, electric and bass.

  Life & fun · 8d ago · guitoro.com

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  See *almost* any carriers phone settings▲432

  Carrier settings from iPhone, Pixel and Galaxy firmware, decoded and compared: APNs, VoLTE, 5G and Wi-Fi Calling per carrier, and what each build changed.

  Life & fun · 12d ago · carrierexplode.com

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  The whole Solar System and every tracked satellite, live in the browser▲407

  Life & fun · 22d ago · space.bl2.net

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  Periscope▲1,049

  Explore the world through someone else's eyes

  Life & fun · 2015 · periscope.tv

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  Product Hunt for Chrome▲898

  The best new products, every day, in your browser

  Life & fun · 2015

• 
  Amazon Dash Button▲772

  Place it. Press it. Get it.

  Commerce · 2015 · amazon.com

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  $Cashtags by Square▲722

  Get paid via $cashtags for things you do online or in person

  Commerce · 2015 · t.co

• 
  Gyroscope▲713

  A new OS for the human body

  Growth · 2015 · gyrosco.pe

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  Freebie.Supply▲669

  Awesome free things for entrepreneurs & startups

  Growth · 2015 · growth.supply