An Advanced Persistent Threat (APT) is a highly sophisticated and prolonged cyberattack campaign typically executed by well-resourced adversaries such as nation-states or organized criminal groups. These attacks target high-value organizations including government agencies, critical infrastructure providers, and enterprises holding sensitive intellectual property. The advanced aspect refers to the use of custom malware, zero-day vulnerabilities, and adaptive evasion techniques designed to bypass conventional security defenses.

The persistent nature of APTs reflects the attacker's determination to maintain long-term access within a target network, often spanning months or years while continuously adapting to defensive countermeasures. Unlike opportunistic attacks, APTs are driven by strategic objectives such as espionage, large-scale data exfiltration, or sabotage. Defending against APTs requires proactive threat intelligence, continuous monitoring, and a comprehensive security strategy to detect and neutralize these complex threats throughout their attack lifecycle.