The detection rule identifies the addition of a privileged user's Security Identifier (SID) to the SID History of another user in Windows Active Directory. This action is significant because it may indicate an attempt to misuse SID history, potentially allowing unauthorized access across domains, privilege escalation, or persistent access. The rule utilizes Windows Event Log Security Events 4742 and 4738, along with identity lookups, to detect such activities. It highlights that the proper configuration of audit policies is necessary for these events to be logged, thereby aiding in the detection of possible malicious activities related to privileged accounts.