Implementing Runtime Security with Tetragon

Overview

Tetragon is a CNCF project under Cilium that provides flexible Kubernetes-aware security observability and runtime enforcement using eBPF. By operating at the Linux kernel level, Tetragon can monitor and enforce policies on process execution, file access, network connections, and system calls with less than 1% performance overhead -- far more efficient than traditional user-space security agents.

When to Use

• When deploying or configuring implementing runtime security with tetragon capabilities in your environment
• When establishing security controls aligned to compliance requirements
• When building or improving security architecture for this domain
• When conducting security assessments that require this implementation

Prerequisites

• Kubernetes cluster v1.24+ with Helm 3.x installed
• Linux kernel 5.4+ (5.10+ recommended for full eBPF feature support)
• kubectl access with cluster-admin privileges
• Familiarity with eBPF concepts and Kubernetes security primitives

Core Concepts

eBPF-Based Security

Tetragon attaches eBPF programs directly to kernel functions, enabling:

• Process lifecycle tracking: Monitor every process creation, execution, and termination across all pods
• File integrity monitoring: Detect unauthorized reads/writes to sensitive files
• Network observability: Track all TCP/UDP connections with full pod context
• System call filtering: Enforce policies on dangerous syscalls like ptrace, mount, or unshare

TracingPolicy Custom Resources

Tetragon uses TracingPolicy CRDs to define what kernel events to observe and what actions to take:

apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: detect-privilege-escalation
spec:
  kprobes:
    - call: "security_bprm_check"
      syscall: false
      args:
        - index: 0
          type: "linux_binprm"
      selectors:
        - matchBinaries:
            - operator: "In"
              values:
                - "/bin/su"
                - "/usr/bin/sudo"
                - "/usr/bin/passwd"
          matchNamespaces:
            - namespace: Pid
              operator: NotIn
              values:
                - "host_ns"
          matchActions:
            - action: Post

Enforcement Actions

Tetragon can take three types of actions directly in the kernel:

1. Sigkill: Immediately terminate the offending process
2. Signal: Send a configurable signal to the process
3. Override: Override the return value of a kernel function to deny an operation

Installation and Configuration

Step 1: Install Tetragon with Helm

helm repo add cilium https://helm.cilium.io
helm repo update

helm install tetragon cilium/tetragon \
  --namespace kube-system \
  --set tetragon.enableProcessCred=true \
  --set tetragon.enableProcessNs=true \
  --set tetragon.grpc.address="localhost:54321"

Step 2: Install the Tetragon CLI

GOOS=$(go env GOOS)
GOARCH=$(go env GOARCH)
curl -L --remote-name-all \
  https://github.com/cilium/tetragon/releases/latest/download/tetra-${GOOS}-${GOARCH}.tar.gz
tar -xzvf tetra-${GOOS}-${GOARCH}.tar.gz
sudo install tetra /usr/local/bin/

Step 3: Verify Installation

kubectl get pods -n kube-system -l app.kubernetes.io/name=tetragon
tetra status

Practical Implementation

Detecting Container Escape Attempts

Create a TracingPolicy to detect processes attempting to escape container namespaces:

apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: detect-container-escape
spec:
  kprobes:
    - call: "__x64_sys_setns"
      syscall: true
      args:
        - index: 0
          type: "int"
        - index: 1
          type: "int"
      selectors:
        - matchNamespaces:
            - namespace: Pid
              operator: NotIn
              values:
                - "host_ns"
          matchActions:
            - action: Sigkill

Monitoring Sensitive File Access

Detect reads of sensitive credentials:

apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: monitor-sensitive-files
spec:
  kprobes:
    - call: "security_file_open"
      syscall: false
      args:
        - index: 0
          type: "file"
      selectors:
        - matchArgs:
            - index: 0
              operator: "Prefix"
              values:
                - "/etc/shadow"
                - "/etc/kubernetes/pki"

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