From cybersecurity-skills
Detects runtime container drift in Kubernetes via Falco rules for binary execution, filesystem changes, configuration deviations, and more. For security incident response and threat hunting.
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Container drift occurs when running containers deviate from their original image state through unauthorized file modifications, unexpected binary execution, configuration changes, or package installations. Since containers should be treated as immutable infrastructure, any drift is a potential indicator of compromise. Detection techniques leverage the DIE (Detect, Isolate, Evict) model -- an im...
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Container drift occurs when running containers deviate from their original image state through unauthorized file modifications, unexpected binary execution, configuration changes, or package installations. Since containers should be treated as immutable infrastructure, any drift is a potential indicator of compromise. Detection techniques leverage the DIE (Detect, Isolate, Evict) model -- an immutable workload should not change during runtime, so any observed change is potentially evidence of malicious activity.
Image-Based Comparison: Compare the running container's filesystem against its source image to identify added, modified, or removed files.
Behavioral Monitoring: Use eBPF or kernel-level monitoring to detect process execution, file access, and network activity that deviates from expected behavior.
Digest Verification: Continuously verify that running container image digests match the approved deployment manifests.
- rule: Drift Detected (Container Image Modified Binary)
desc: Detect execution of a binary not present in the original container image
condition: >
spawned_process and
container and
not proc.pname in (container_entrypoint) and
proc.is_exe_upper_layer = true
output: >
Drift detected: new binary executed in container
(user=%user.name command=%proc.cmdline container=%container.name
image=%container.image.repository:%container.image.tag
exe_path=%proc.exepath)
priority: WARNING
tags: [container, drift]
- rule: Container Shell Spawned
desc: Detect interactive shell in a container that should be immutable
condition: >
spawned_process and
container and
proc.name in (bash, sh, dash, zsh, csh, ksh) and
not proc.pname in (container_entrypoint)
output: >
Shell spawned in container (user=%user.name shell=%proc.name
container=%container.name image=%container.image.repository)
priority: WARNING
tags: [container, drift, shell]
- rule: Package Manager Execution in Container
desc: Detect use of package managers indicating drift
condition: >
spawned_process and
container and
proc.name in (apt, apt-get, yum, dnf, apk, pip, pip3, npm, gem, cargo)
output: >
Package manager executed in container (user=%user.name
command=%proc.cmdline container=%container.name
image=%container.image.repository)
priority: ERROR
tags: [container, drift, package-manager]
- rule: Container File System Write
desc: Detect writes to container upper layer filesystem
condition: >
open_write and
container and
fd.typechar = 'f' and
not fd.name startswith /tmp and
not fd.name startswith /var/log and
not fd.name startswith /proc
output: >
File write in container (user=%user.name file=%fd.name
container=%container.name)
priority: NOTICE
tags: [container, drift, filesystem]
Prevent drift by making container filesystems immutable:
apiVersion: apps/v1
kind: Deployment
metadata:
name: immutable-app
spec:
template:
spec:
containers:
- name: app
image: app:v1.0@sha256:abc123...
securityContext:
readOnlyRootFilesystem: true
allowPrivilegeEscalation: false
runAsNonRoot: true
volumeMounts:
- name: tmp
mountPath: /tmp
- name: cache
mountPath: /var/cache
volumes:
- name: tmp
emptyDir:
sizeLimit: 100Mi
- name: cache
emptyDir:
sizeLimit: 50Mi
apiVersion: v1
kind: Namespace
metadata:
name: production
labels:
pod-security.kubernetes.io/enforce: restricted
pod-security.kubernetes.io/audit: restricted
pod-security.kubernetes.io/warn: restricted
#!/bin/bash
# Compare running container digests against approved manifest
NAMESPACE="production"
kubectl get pods -n "$NAMESPACE" -o json | jq -r '
.items[] |
.spec.containers[] |
"\(.image) \(.imageID)"
' | while read IMAGE IMAGE_ID; do
APPROVED_DIGEST=$(kubectl get deploy -n "$NAMESPACE" -o json | \
jq -r ".items[].spec.template.spec.containers[] | select(.image==\"$IMAGE\") | .image")
if [[ "$IMAGE" != *"@sha256:"* ]]; then
echo "[WARN] Container using mutable tag: $IMAGE"
fi
done
For Azure Kubernetes environments, Microsoft Defender provides built-in binary drift detection:
{
"alertType": "K8S.NODE_ImageBinaryDrift",
"severity": "Medium",
"description": "Binary executed that was not part of the original container image",
"remediationSteps": [
"Investigate the binary origin and purpose",
"Check if the container was compromised",
"Rebuild the container from a clean image",
"Enable readOnlyRootFilesystem"
]
}