Security testing is a process to determine if an information system protects data and maintains functionality. It checks for data leakage and unauthorized access. The main purposes of security testing are to identify vulnerabilities and repair them to improve security and ensure the system remains secure over time. Some common security testing techniques include vulnerability scanning, security scanning, penetration testing, ethical hacking, risk assessment, security auditing, and password cracking. These techniques help evaluate security posture and find weaknesses in operating systems, applications, networks, and passwords. Security testing should be included in software development to help ensure quality and security.