what is a threat actor (or malicious actor)?

Brief Explanations:

A threat actor or malicious actor is an individual or entity that attempts to gain unauthorized access to a system, network, or data with malicious intent, such as stealing information, causing damage, or disrupting operations.

Answer:

A threat actor (or malicious actor) is an individual or entity that attempts unauthorized access with malicious intent to systems, networks, or data for purposes like theft, damage, or disruption.