In early 2023, the Cybersecurity and Infrastructure Security Agency (CISA) conducted a SILENTSHIELD red team assessment against a Federal Civilian Executive Branch (FCEB) organization. During SILENTSHIELD assessments, the red team first performs a no-notice, long-term simulation of nation-state cyber operations. The team mimics the techniques, tradecraft, and behaviors of sophisticated threat actors and measures the potential dwell time actors have on a network, providing a realistic assessment of the organization’s security posture. Then, the team works directly with the organization’s network defenders, system administrators, and other technical staff to address strengths and weaknesses found during the assessment. The team’s goal is to assist the organization with refining their detection, response, and hunt capabilities—particularly hunting unknown threats.