Basic Terms Threat,vulnerability,attack,and intrusion Threat:attackers,angry employees,etc. Vulnerability:weakness of a system Attack:actions to make harm to a system by modifying the system,reading information from the system,or stopping the system from serving its legitimate users -Passive attacks:read information in a system ●e.g,Eavesdropping -Active attacks:modify a system e.g.,message modification,insertion,deletion,replay Intrusion:successfully modifying a system or reading information from the system 22 Basic Terms  Threat, vulnerability, attack, and intrusion  Threat: attackers, angry employees, etc.  Vulnerability: weakness of a system  Attack: actions to make harm to a system by modifying the system, reading information from the system, or stopping the system from serving its legitimate users ─ Passive attacks: read information in a system ● e.g., Eavesdropping ─ Active attacks: modify a system ● e.g., message modification, insertion, deletion, replay  Intrusion: successfully modifying a system or reading information from the system