Packet capture best practices encompass the strategies, architectures, and operational procedures for reliably collecting network traffic data for security monitoring, forensic investigation, and troubleshooting. Effective packet capture requires balancing comprehensive visibility with storage constraints, privacy requirements, and performance impacts.
Packet capture architecture begins with tap placement strategy. Network TAPs provide passive, reliable access to traffic without impacting the monitored link. SPAN (mirror) ports offer flexibility but can drop packets under load and miss errors. Capture points are prioritized at network boundaries, between security zones, in front of critical assets, and at core aggregation points. Capture systems must be sized for sustained traffic rates with headroom for bursts. Ring buffers automatically overwrite oldest data when storage fills, with event-triggered full capture preserving traffic around security incidents. BPF (Berkeley Packet Filter) expressions focus capture on relevant traffic, reducing storage requirements. Time synchronization via NTP or PTP across all capture points enables accurate correlation. PCAP file rotation with consistent naming conventions and hash verification ensures manageability and integrity. Encryption of stored captures protects sensitive data at rest. Retention policies balance investigative needs with storage costs and privacy regulations. Automated indexing enables rapid retrieval of specific traffic during investigations.
Without pre-positioned capture infrastructure, organizations cannot perform network forensics when incidents occur. Deploying capture capabilities during an active incident is too late as critical traffic has already passed. The difference between a thorough investigation and an inconclusive one often comes down to whether packet data was available. Proper capture practices also support real-time security monitoring, performance troubleshooting, and compliance validation.
CDA addresses packet capture within the Threat Intelligence and Defense domain as a forensic readiness component. Our missions design capture architectures, specify hardware requirements, establish retention policies, and validate that capture infrastructure provides the visibility needed for effective security monitoring and incident investigation.