An advanced persistent threat (APT) is a covert cyber attack on a computer network where the attacker gains and maintains unauthorized access to the targeted network and remains undetected for a significant period. During the time between infection and remediation the hacker will often monitor, intercept, and relay information and sensitive data. The intention of an APT is to exfiltrate or steal data rather than cause a network outage, denial of service or infect systems with malware.
APTs often use social engineering tactics or exploit software vulnerabilities in organizations with high value information.