Upon identification of an indicator of compromise (IoC) associated with an APT actor, the risk practitioner's best course of action is to assess the adequacy of existing security controls. This involves evaluating whether current defenses are sufficient to detect, prevent, and respond tosuch sophisticated threats. Ensuring control effectiveness is vital to mitigating the risk posed by APTs.CISA Reference:ISACA CRISC Review Manual, 7th Edition, Chapter 4: Information Technology and Security, Section: Threat and Vulnerability Management.