 Hello, my name is Aikopras. In this video, we will introduce some terminology as used throughout our lectures on internet security. In particularly, we will introduce the following six terms, vulnerability, threat, attack, exploit, security service and security mechanism. We define the term vulnerability as a weakness in the design, implementation or operation of networks or connected systems that could be exploited to compromise security. And we define the term threat as the danger that emerges once potential vulnerabilities become known and there are people willing and able to exploit that vulnerability. The term attack denotes an action that compromises the security of networks and connected systems. And the term exploit is used to denote a piece of software or a sequence of commands that take advantage of a vulnerability to compromise the security of networks or connected systems. Finally, we define two additional terms. The term security service is used to denote a quality or facility of the network, system or information exchanges that is obtained once security mechanisms are implemented. And the term security mechanism is used to denote a set of rules or protocols that are designed to prevent, detect or recover from a security attack. In this video, we have defined some key terminology in the area of internet security. Note that we also have a series of videos that discuss in detail attacks as well as security services.