CTF

Capture the Flag (CTF) is a type of cybersecurity competition in which participants solve security-focused challenges to earn points. In most CTFs, a correct solution yields a flag, a piece of data that proves the challenge was completed. Flags are typically strings extracted from systems, binaries, or networks and submitted to a scoring server for verification.

CTF formats generally fall into two broad categories: Jeopardy-style and Attack-Defence. In Jeopardy-style events, challenges are organized into categories such as cryptography, reverse engineering, web security, forensics, and binary exploitation, each assigned a point value. Teams choose tasks, publish solutions, and accumulate points. In Attack-Defence events, teams operate vulnerable services, defending their own machines while attempting to compromise opponents’ services to obtain their flags.

Challenges range from beginner to expert and can include tasks like breaking encryption, debugging programs, reading disassembled code, web application testing, memory analysis, and network traffic scavenging. Most CTFs provide write-ups or hints after participation to aid learning. Scoring is typically handled by a central server that validates flags and updates standings in real time.

CTFs are organized by universities, security communities, and industry groups, and are held both online and at conferences. Notable events include DEF CON Capture the Flag, CSAW, Google CTF, and picoCTF. These competitions are used to teach practical skills, recruit talent, and foster collaboration among security researchers and students.

Participation ranges from individuals to multi-person teams, with many educational platforms offering beginner tracks and practice problems. CTF activity is widely recognized as a hands-on approach to learning offensive and defensive security techniques.