The rule 'Cisco Secure Firewall - Potential Data Exfiltration' is designed to detect large outbound data transfers that may indicate unauthorized data exfiltration. It utilizes Cisco Secure Firewall Threat Defense logs to analyze the volume of data exchanged via network connections. Specifically, it sums the InitiatorBytes and ResponderBytes for each connection and flags any instance where the total volume exceeds 100 MB. This threshold is significant as it might suggest the staging of sensitive data for unauthorized exfiltration, particularly when the transfer originates from unusual users or processes. The detection logic is constrained to internal to external network flows using a specific macro, enhancing the accuracy of the rule by abstracting environment-specific configurations. The potential for false positives exists, particularly during legitimate activities such as backups or synchronization, necessitating additional user context evaluation to verify suspicious activity.