Nowdays cybersecurity is a very important field, thanks to global spread of Internet and smart devices, demand for cybersecurity expert is continuously growing, so computer security education has become a priority. Together with security courses, security competitions are a very important tool which can be used for educational purposes. Capture the Flag (CTF) competitions are most popular type of security competitions, because playing them contestants, grouped in teams, can improve their teamwork, and can apply, test and demonstrate practically their skills and theoretical knowledge learned in security courses, by solving challenges and/or exploiting vulnerabilities. In particular, in Attack/Defense CTF, contestants have to interact and challenge each other, by exploiting services of other teams while they are patching their own services, focusing on both attack and defense and developing offensive and defensive skills.