This detection rule identifies unusual DLL calls made by the Spooler service (spoolsv.exe), which is known to have critical vulnerabilities. Specifically, it targets rare DLL usage that may indicate malicious activity, tying back to real-world exploits such as CVE-2021-1675 (PrintNightmare). The logic relies on Windows Event Code 4663, which must be enabled for auditing to capture file access events related to DLLs in the Spooler driver directory. The rule processes events to evaluate the frequency and origin of the DLL calls, alerting on less common occurrences from unique hosts, helping detect potential exploitation attempts by known threat actors like Vice Society and various ransomware groups.