An Advanced Persistent Threat is a long-term intrusion campaign run by a capable, often well-funded actor that aims to stay covert, maintain access, and avoid detection. The “advanced” part refers to the attacker’s tradecraft, which may include custom malware, living-off-the-land techniques, proxying, and abuse of legitimate cloud services. The “persistent” part means the operator keeps trying to re-enter, expand access, or preserve a foothold over time.
APTs matter because they are usually built for espionage, sabotage, or quiet data theft rather than immediate disruption. In real intrusions, defenders may see normal-looking traffic used for command-and-control, such as trusted APIs, collaboration tools, SOCKS relays, or tunnels that blend into everyday network noise. Detection therefore depends on correlation across identity, endpoint, and cloud logs, plus attention to unusual authentication patterns, API use, and hidden relay infrastructure. An APT is less about one exploit than about sustained control of the environment.