Teaching ethical hacking techniques is fundamental to security education and allows students to better understand the ways in which computer and network systems fail. This paper discusses the implementation of comprehensive offensive hands-on lab exercises about four common Denial of Service (DoS) attacks. Moreover, the paper discusses the implementation of a defense technique against the DoS attacks using Snort tool, as an intrusion detection system. The impact of offering the exercises on the student performance in terms of achieving the course outcomes is also discussed. Although a significant improvement in the student performance has been observed, a major ethical concern has been identified when teaching ethical hacking techniques. As a consequence, the paper lists a number of steps that should be taken by schools and educators to reduce the liability of teaching ethical hacking techniques in information security curriculum.