The 'Suspicious Spool Authentication' detection rule identifies potential NTLM relay attacks that exploit vulnerabilities in the SpoolService. By observing specific Windows Event Logs, particularly Event IDs 4624 (successful logon) and 5145 (file share access), the rule captures instances where NTLM authentication is used and where spooler services are involved. This behavior can indicate attempts to relay authentication requests through the spool service, which is notably associated with credential access techniques. The logic leverages Splunk commands to filter relevant events, group them by time intervals, and check for multiple source IP addresses to detect unusual patterns. The expected outcome is to flag events that suggest exploitation of the SpoolService and NTLM relay capabilities, alerting security teams to investigate potential adversary tactics related to lateral movement or credential theft.