An advanced persistent threat (APT) is a stealthy and sophisticated attack that aims to compromise and maintain access to a target network or system over a long period of time, often for espionage or sabotage purposes. APTs are difficult to detect by conventional security tools, such as antivirus or firewalls, that rely on signatures or rules to identify threats. Therefore, the best way to monitor for APTs is to search for anomalies in the environment, such as unusual network traffic, user behavior, file activity, or system configuration changes, that may indicate a compromise or an ongoing attack. References: https://www.isaca.
org/credentialing/cism https://www.nist.gov/publications/information-security-handbook-guide-managers