GCP-NET - VPC Flow - Connection to Rare External Destination
This rule monitors GCP VPC Flow logs for potential command and control (C2) or data exfiltration activity by identifying internal-to-external network connections that exhibit high novelty. It calculates the percentage of new destination IP addresses contacted by internal source IPs within a single day. Alerts are triggered when a source IP initiates connections to at least 20 unique external destinations, where at least 20% of those destinations have never been contacted by that source in the previous day. This behavioral analysis is designed to detect reconnaissance, scanning, or large-scale data exfiltration patterns.
Sigma
