Tech Matchups: VPC Flow Logs vs Traffic Mirroring
Overview
VPC Flow Logs capture metadata about IP traffic entering and leaving VPC resources, providing insights into network activity and security.
Traffic Mirroring duplicates and sends packet-level data from VPC resources to monitoring tools for deep inspection and analysis.
Both enable network monitoring: Flow Logs for high-level metadata, Traffic Mirroring for detailed packet analysis.
Section 1 - Functionality and Data Capture
VPC Flow Logs record metadata (e.g., source/destination IPs, ports, protocols) for traffic at VPC, subnet, or ENI levels—e.g., logging TCP 80 traffic to an EC2 instance. Outputs to CloudWatch or S3.
Traffic Mirroring captures full packet data (headers and payloads)—e.g., mirroring HTTP requests from an ENI to an NLB for analysis. Sends to EC2 or NLB targets.
Scenario: Flow Logs for traffic pattern analysis; Traffic Mirroring for intrusion detection.
Section 2 - Analysis Depth and Use Cases
Flow Logs provide high-level insights—e.g., detecting unusual traffic spikes (10K connections to port 22). Ideal for compliance, troubleshooting, or anomaly detection.
Traffic Mirroring enables deep packet inspection—e.g., analyzing HTTP payloads for malware signatures. Suits security forensics, protocol debugging, or advanced threat detection.
Scenario: Flow Logs identify a DDoS attack’s source; Traffic Mirroring inspects packets for SQL injection. Flow Logs are broad; Traffic Mirroring is granular.
Section 3 - Cost and Scalability
Flow Logs cost based on storage and processing—e.g., $0.50/GB for CloudWatch Logs or $0.023/GB for S3 in us-east-1. Example: 1TB/month in S3 costs ~$23.60.
Traffic Mirroring incurs data transfer costs ($0.01/GB in-VPC) and target resource costs (e.g., EC2 or NLB). Example: 1TB/month to an NLB costs ~$10.24 (data) + NLB fees (~$16.20).
Flow Logs scale to all VPC traffic; Traffic Mirroring scales to specific ENIs, limited by target capacity.
Scenario: Flow Logs for broad monitoring; Traffic Mirroring for targeted deep dives.
Section 4 - Integration and Management
Flow Logs integrate with CloudWatch for real-time analysis—e.g., triggering alarms on suspicious traffic—or S3 for long-term storage. Simple to enable, low management overhead.
Traffic Mirroring requires setup of mirror sessions, filters, and targets—e.g., configuring an NLB to forward packets to an IDS tool. Higher complexity, needs monitoring tools.
Scenario: Flow Logs for automated compliance reports; Traffic Mirroring for custom security tools. Flow Logs are easier; Traffic Mirroring is intensive.
Section 5 - Comparison Table
| Aspect | VPC Flow Logs | Traffic Mirroring |
|---|---|---|
| Data Type | Metadata | Full Packets |
| Analysis | Broad Patterns | Deep Inspection |
| Cost | Storage-Based | Data + Target |
| Integration | CloudWatch, S3 | EC2, NLB |
| Best For | Compliance, Trends | Security Forensics |
Flow Logs for overview, Traffic Mirroring for detail. Use both for robust monitoring.
Conclusion
VPC Flow Logs and Traffic Mirroring provide complementary network monitoring capabilities. Flow Logs offer high-level metadata for traffic analysis, ideal for compliance and anomaly detection. Traffic Mirroring delivers packet-level insights, perfect for security forensics and advanced threat detection.
Weigh depth (metadata vs. packets), cost (storage vs. processing), and complexity (simple vs. intensive). Use Flow Logs for broad visibility, Traffic Mirroring for targeted analysis—or combine: Flow Logs for trends, Traffic Mirroring for deep security investigations.