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detecting-container-escape-with-falco-rules Write and tune Falco rules that monitor Linux syscalls to detect container escape techniques in real time, including host filesystem mounts, sensitive host path access, kernel module loading, and abuse of privileged container capabilities. Use when deploying or tuning Falco for a Kubernetes/container environment, or when investigating an alert tied to syscall-level escape behavior.
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name detecting-container-escape-with-falco-rules description Write and tune Falco rules that monitor Linux syscalls to detect container escape techniques in real time, including host filesystem mounts, sensitive host path access, kernel module loading, and abuse of privileged container capabilities. Use when deploying or tuning Falco for a Kubernetes/container environment, or when investigating an alert tied to syscall-level escape behavior. domain cybersecurity subdomain container-security tags ["falco","container-escape","runtime-security","syscall-monitoring","kubernetes","detection"] version 1.0 author mahipal license Apache-2.0 d3fend_techniques ["Token Binding","Execution Isolation","File Metadata Consistency Validation","Restore Access","Application Protocol Command Analysis"] nist_csf ["PR.PS-01","PR.IR-01","ID.AM-08","DE.CM-01"] mitre_attack ["T1610","T1611","T1609","T1525","T1068"]
Detecting Container Escape with Falco Rules
Overview
Falco is a CNCF-graduated runtime security tool that monitors Linux syscalls to detect anomalous container behavior. It uses a rules engine to identify container escape techniques such as mounting host filesystems, accessing sensitive host paths, loading kernel modules, and exploiting privileged container capabilities.
When to Use
When investigating security incidents that require detecting container escape with falco rules
When building detection rules or threat hunting queries for this domain
When SOC analysts need structured procedures for this analysis type
When validating security monitoring coverage for related attack techniques
Prerequisites
Linux host with kernel 5.8+ (for eBPF driver) or kernel module support
Kubernetes cluster (v1.24+) or standalone Docker/containerd
Helm 3 for Kubernetes deployment
Root or privileged access for driver installation
Installing Falco
Kubernetes Deployment with Helm
helm repo add falcosecurity https://falcosecurity.github.io/charts
helm repo update
helm install falco falcosecurity/falco \
--namespace falco --create-namespace \
--set falcosidekick.enabled=true \
--set falcosidekick.webui.enabled=true \
--set driver.kind=ebpf \
--set collectors.containerd.enabled=true \
--set collectors.containerd.socket=/run/containerd/containerd.sock
kubectl get pods -n falco
kubectl logs -n falco -l app.kubernetes.io/name=falco --tail =20
Standalone Installation (Debian/Ubuntu)
curl -fsSL https://falco.org/repo/falcosecurity-packages.asc | \
sudo gpg --dearmor -o /usr/share/keyrings/falco-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/falco-archive-keyring.gpg] https://download.falco.org/packages/deb stable main" | \
sudo tee /etc/apt/sources.list.d/falcosecurity.list
sudo
sudo
sudo
enable
sudo
Container Escape Detection Rules
Rule 1: Detect Host Mount from Container - rule: Container Mounting Host Filesystem
desc: Detect a container attempting to mount the host filesystem
condition: >
spawned_process and container and
proc.name = mount and
(proc.args contains "/host" or proc.args contains "nsenter")
output: >
Container mounting host filesystem
(user=%user.name container_id=%container.id container_name=%container.name
image=%container.image.repository command=%proc.cmdline %evt.args)
priority: CRITICAL
tags: [container , escape , T1611 ]
Rule 2: Detect nsenter Usage (Namespace Escape) - rule: Nsenter Execution in Container
desc: Detect nsenter being used to escape container namespaces
condition: >
spawned_process and container and proc.name = nsenter
output: >
nsenter executed in container - potential escape attempt
(user=%user.name container_id=%container.id image=%container.image.repository
command=%proc.cmdline parent=%proc.pname)
priority: CRITICAL
tags: [container , escape , namespace , T1611 ]
Rule 3: Detect Privileged Container Launch - rule: Launch Privileged Container
desc: Detect a privileged container being launched
condition: >
container_started and container and container.privileged=true
output: >
Privileged container started
(user=%user.name container_id=%container.id container_name=%container.name
image=%container.image.repository)
priority: WARNING
tags: [container , privileged , T1610 ]
Rule 4: Detect /proc/sysrq-trigger Write - rule: Write to Sysrq Trigger
desc: Detect writes to /proc/sysrq-trigger which can crash or control the host
condition: >
open_write and container and fd.name = /proc/sysrq-trigger
output: >
Write to /proc/sysrq-trigger from container
(user=%user.name container_id=%container.id image=%container.image.repository
command=%proc.cmdline)
priority: CRITICAL
tags: [container , escape , host-manipulation ]
Rule 5: Detect Kernel Module Loading from Container - rule: Container Loading Kernel Module
desc: Detect a container attempting to load a kernel module
condition: >
spawned_process and container and
(proc.name in (insmod, modprobe) or
(proc.name = init_module))
output: >
Kernel module loading from container
(user=%user.name container_id=%container.id image=%container.image.repository
command=%proc.cmdline)
priority: CRITICAL
tags: [container , escape , kernel , T1611 ]
Rule 6: Detect Container Breakout via cgroups - rule: Write to Cgroup Release Agent
desc: Detect writes to cgroup release_agent which is a known container escape vector
condition: >
open_write and container and
fd.name endswith release_agent
output: >
Container writing to cgroup release_agent - escape attempt
(user=%user.name container_id=%container.id image=%container.image.repository
file=%fd.name command=%proc.cmdline)
priority: CRITICAL
tags: [container , escape , cgroup , CVE-2022-0492 ]
Rule 7: Detect Access to Host /etc/shadow - rule: Container Reading Host Shadow File
desc: Detect a container reading /etc/shadow on the host via mounted volume
condition: >
open_read and container and
(fd.name = /etc/shadow or fd.name startswith /host/etc/shadow)
output: >
Container reading host shadow file
(user=%user.name container_id=%container.id image=%container.image.repository
file=%fd.name command=%proc.cmdline)
priority: CRITICAL
tags: [container , credential-access , T1003 ]
Rule 8: Detect Docker Socket Access - rule: Container Accessing Docker Socket
desc: Detect a container accessing the Docker socket which allows host control
condition: >
(open_read or open_write) and container and
fd.name = /var/run/docker.sock
output: >
Container accessing Docker socket
(user=%user.name container_id=%container.id image=%container.image.repository
command=%proc.cmdline)
priority: CRITICAL
tags: [container , escape , docker-socket , T1610 ]
Complete Custom Rules File
- list: escape_binaries
items: [nsenter , chroot , unshare , mount , umount , pivot_root ]
- macro: container_escape_attempt
condition: >
spawned_process and container and
proc.name in (escape_binaries)
- rule: Container Escape Binary Execution
desc: Detect execution of binaries commonly used for container escape
condition: container_escape_attempt
output: >
Escape-related binary executed in container
(user=%user.name container=%container.name image=%container.image.repository
command=%proc.cmdline parent=%proc.pname pid=%proc.pid)
priority: CRITICAL
tags: [container , escape , mitre_T1611 ]
- rule: Sensitive File Access from Container
desc: Detect container access to sensitive host files
condition: >
(open_read or open_write) and container and
(fd.name startswith /proc/1/ or
fd.name = /etc/shadow or
fd.name = /etc/kubernetes/admin.conf or
fd.name startswith /var/lib/kubelet/)
output: >
Sensitive file accessed from container
(container=%container.name image=%container.image.repository
file=%fd.name command=%proc.cmdline user=%user.name)
priority: CRITICAL
tags: [container , sensitive-file , mitre_T1005 ]
Falco Configuration
rules_files:
- /etc/falco/falco_rules.yaml
- /etc/falco/rules.d/container-escape.yaml
json_output: true
json_include_output_property: true
json_include_tags_property: true
log_stderr: true
log_syslog: true
log_level: info
priority: WARNING
stdout_output:
enabled: true
syslog_output:
enabled: true
http_output:
enabled: true
url: http://falcosidekick:2801
insecure: true
grpc:
enabled: true
bind_address: "unix:///run/falco/falco.sock"
threadiness: 8
grpc_output:
enabled: true
Alert Integration
Forward to Slack via Falcosidekick
config:
slack:
webhookurl: "https://hooks.slack.com/services/XXXXX"
minimumpriority: "warning"
messageformat: |
*{{.Priority}}* - {{.Rule}}
Container: {{.OutputFields.container_name}}
Image: {{.OutputFields.container_image_repository}}
Command: {{.OutputFields.proc_cmdline}}
Testing Rules
kubectl run test-escape --image=alpine --restart=Never -- sh -c "cat /etc/shadow"
kubectl run test-nsenter --image=alpine --restart=Never --overrides='{"spec":{"hostPID":true}}' -- nsenter -t 1 -m -u -i -n -- cat /etc/hostname
kubectl logs -n falco -l app.kubernetes.io/name=falco --tail =50 | grep -i escape
Best Practices
Deploy Falco as DaemonSet to ensure coverage on all nodesUse eBPF driver over kernel module for safer operationStart with default rules (maturity_stable) then add custom rulesForward alerts to SIEM/SOAR via FalcosidekickTag rules with MITRE ATT&CK technique IDs for correlationTest rules in permissive mode before enforcingTune false positives by adding exception lists for known good processesMonitor Falco health with Prometheus metrics endpoint 