Threat Actor: According to Tech Target, a threat actor, also called a malicious actor, is an entity that is partially or wholly responsible for a security incident that impacts – or has the potential to impact – an organization's security. Hacker: According to Wikipedia, In computing, a hacker is any skilled computer expert that uses their technical knowledge to overcome a problem. While hacker can refer to any computer programmer, the term has become associated in popular culture with a security hacker, someone who, with their technical knowledge, uses bugs or exploits to break into computer systems. Attacker: According to Wikipedia, In computer and computer networks an attack is any attempt to destroy, expose, alter, disable, steal or gain unauthorized access to or make unauthorized use of an asset. Thus, an attacker is the individual or organization performing these malicious activities.