The threat detection rule titled "FirstTime Seen Account Performing DCSync" aims to identify when a user account initiates the Active Directory replication process for the first time. This is particularly critical because attackers can employ the DCSync technique, which allows them to retrieve credential material from domain controllers, potentially compromising the entire domain. The rule activates upon monitoring Windows Event ID 4662, which indicates that an operation was performed on an Active Directory object, specifically looking for access masks corresponding to the replication privileges. The rule also notifies when the replication request has not been seen within the last 15 days, thus indicating anomalous behavior. It emphasizes the dangers of unauthorized DCSync operations and suggests thorough investigations when such events occur, including user account legitimacy checks and credential exposure assessments.