The 'Cisco Secure Firewall - Lumma Stealer Activity' rule is designed to detect Lumma Stealer malware activity through the analysis of Cisco Secure Firewall Intrusion Events. It operates by examining logs from Cisco Secure Firewall Threat Defense, focusing on the occurrence of specific Snort signature IDs associated with Lumma Stealer within a 15-minute window from the same host. The rule identifies cases where at least three of these signature IDs (ranging from 64793 to 64812) are logged, which can indicate a potential compromise. The design not only highlights the necessary event types and signature IDs, but also incorporates a search query tailored for the Splunk environment, emphasizing the need for correct indexing and log configurations. False positives are reported as unlikely, making this detection rule a critical component for monitoring network security and responding to Lumma Stealer threats.