attacker

An attacker is a person or organization that conducts an attack, an intentional act intended to cause harm, damage, or unauthorized access. The term is used across contexts such as military operations, sports, and information security.

In military and law enforcement, an attacker is the force or unit that advances toward objectives, seeks to overwhelm defenses, or inflict harm, while subject to rules of engagement and international law. In sports, the attacker—often a forward or offensive player—focuses on scoring, creating scoring opportunities, or breaking through the opponent’s defense, within the rules and structure of the game.

In information security, an attacker, also called a threat actor or intruder, seeks to gain unauthorized access, steal data, disrupt services, or cause other harm. Attacker types include opportunistic actors, who exploit common vulnerabilities; targeted actors, who pursue specific victims or data; and state-sponsored or organized groups. Attacks are usually described in stages such as reconnaissance, intrusion attempts, exploitation, and, if successful, persistence or data exfiltration. Defenders employ measures such as access controls, monitoring, segmentation, and incident response to deter, detect, and mitigate attacks.

Legal and ethical considerations vary by jurisdiction but generally treat unauthorized access or damage as criminal offenses. Responsibility may depend on intent, means, and the resulting harm. The term remains neutral, used to describe a participant in harm-inflicting actions across domains, with emphasis on prevention, detection, and accountability.