What Is a Sidecar Scan? A Simple Guide to Container Traffic Monitoring

 Sidecar Scan

A sidecar scan typically refers to a network-monitoring or security technique that uses the sidecar design pattern to observe and analyze traffic in containerized environments, especially in Kubernetes or microservice architectures.

What Is a Sidecar?

In software architecture, a sidecar is a secondary container or process that runs alongside a primary application container. It shares the same host or pod but operates independently, handling auxiliary tasks such as:

• Logging
• Monitoring
• Security
• Configuration
• Network traffic analysis

What Is a Sidecar Scan?

A sidecar scan involves deploying a sidecar container specifically designed to monitor, intercept, and analyze network traffic to and from the main application container. This is commonly used for:

• Security auditing
• Threat detection (e.g., DDoS, port scans)
• Telemetry collection
• Policy enforcement

The scan is non-intrusive, meaning it doesn’t interfere with the main application’s logic or performance. Instead, it observes traffic passively or actively from within the same pod or host.

Use Cases in Cybersecurity

1. eBPF-based Sidecar Scanning

• Uses eBPF (Extended Berkeley Packet Filter) programs inside sidecars to inspect traffic at the kernel level.
• Enables fine-grained Layer 4 and Layer 7 policy enforcement.
• Detects anomalies like unauthorized access or unusual traffic patterns.

2. Kubernetes Network Monitoring

• Sidecars can sniff traffic between containers in a pod.
• Useful in managed environments (e.g., AWS EKS, GKE) where direct access to nodes is restricted.
• Traffic can be filtered, encrypted, and tunneled for analysis.

 How It Works

• The sidecar container is added to the pod via a deployment configuration (e.g., YAML file).
• It shares the network namespace with the main container, allowing it to see all traffic.
• It can log, mirror, or forward traffic to a central analysis system.
• It can be configured to use minimal resources (e.g., 0.25 vCPU and 256 MB of RAM).

Benefits

• Isolation of concerns: Keeps monitoring logic separate from business logic.
• Security: Reduces attack surface and enables real-time threat detection.
• Scalability: Sidecars can be scaled independently.
• Flexibility: Easily added or removed without modifying the main app.