Security basics: definitions of threat, attack, and vulnerability

Often the terms threat, attack, and vulnerability are interchanged and misused. Each is defined here.

Definition of threat: the expressed potential for the occurrence of a harmful event such as an attack.

Definition of attack: an action taken against a target with the intention of doing harm.

Definition of vulnerability: a weakness that makes targets susceptible to an attack.

Excerpt from CISSP Guide to Security Essentials, chapter 10