Container Security Checklist: Importance & Mistakes

In an indirect interpretation of Kerckhoff’s principle in cryptography – a cryptographic system should remain secure even if everything about the system, except the key, is known to the attacker.

This principle is the foundation of an important truth about modern security, which is obscurity is not necessarily protection. Similarly, containerization, a powerful tool in modern software deployment may prevent lateral moves within a network if implemented correctly, but it doesn’t stop an app inside the container from being compromised.

Containers package convenience, but without strong security, they also package risk. Not shockingly, 60% of container images running in production environments are riddled with known vulnerabilities creating an open door for cyber threats.

So how do you safeguard your containers from potential breaches? The answer starts with a comprehensive container security checklist that addresses vulnerabilities at every layer, ensuring that no gap is left exposed.

In this post, we share with you a container security checklist and some of the best practices that will help you create an impenetrable fort to secure your containers.

What is Container Security?

Container security is the process of protecting containerized applications, along with the infrastructure that supports them, from vulnerabilities and threats throughout their lifecycle.

This includes securing the entire stack, from the container engine, the host operating system, and the orchestration platform (like Kubernetes) to the containers themselves.

A key part of container security is continuous scanning, starting from the base images to the application code within containers.

You should actively monitor for runtime risks that may indicate an attack while ensuring that container images used are from trusted sources and free from known vulnerabilities.

You must also execute the isolation of the container flawlessly. Double-check for any weak spots—privilege escalation, wrongly configured networks, and so on.

There are several other measures that you can take to actively rid your environment of threats. With a strong set of container security protocols or checklists that include a range of practices, tools, and policies, you can safeguard the entire container lifecycle—from development and deployment to runtime and decommissioning.

Importance of a Container Security Checklist

Container environments are a labyrinth of moving parts. And if you want to manage their security, you need a system. Keeping guidelines or checklists handy can cut down on the time of successfully deploying a fully secured Docker or Kubernetes container.

Apart from saving time, a security checklist has several other perks:

1. Standardization: Standardizing every step of the container lifecycle is key to ensuring uniformity and preventing critical mistakes. When people work together, there’s always the chance for human error. Having clear guidelines on tasks keeps everyone on the same page and helps things run smoothly.
2. Comprehensive coverage: Containerized environments have multiple building blocks, such as images, registries, networks, and runtime. Running a check before these elements are brought into the system should be mandatory. This might include image scanning, access controls, network segmentation, and runtime monitoring.
3. Efficiency and consistency: A checklist is just another step in guaranteeing a secured container, giving your operations the extra edge toward efficacy and consistency. Moreover, your teams will have a point of reference on security best practices, thereby reducing their chances of missing a step.
4. Compliance: Given the increasing number of cyber threats and data breaches, governments and regulatory bodies have laid down stringent regulatory requirements. A well-defined container security checklist helps ensure compliance by enforcing best practices like role-based access control (RBAC), image scanning, and adhering to CIS benchmarks for Docker and Kubernetes. It also ensures logs and monitors for audits and meets the requirements of frameworks like GDPR, HIPAA, or PCI-DSS.
5. Proactive threat mitigation: It is always a good idea to go through the entire container lifecycle twice before deploying it, and a checklist helps you achieve that. The first pass ensures all security measures are implemented, while the second serves as a validation step to catch any missed configurations or emerging threats before they become critical issues.

The 10 Key Container Security Checklists

Now that we have established the importance of the container security checklist, it is time to dig deeper and understand which security checks you must implement.

Here is a Docker and Kubernetes security checklist that concisely lists all the steps your security protocol must have:

1. Image Security

•  Use trusted and verified base images from official repositories.
•  Restrict who can push/pull images to/from the registry
•  Regularly scan container images for vulnerabilities.
•  Block deployment of vulnerable images or limit their network access
•  Detect sensitive data like keys or tokens before pushing images
•  Ensure images are minimal, containing only necessary dependencies.
•  Implement automated image patching and updates.

2. Access and Permissions

•  Avoid running containers with root privileges.
• Prevent containers from gaining excessive privileges or making unnecessary system calls.
•  Implement the principle of least privilege for containers and users.
•  Control which containers can modify specific files or directories.
• Use PodSecurity Admission to restrict access to sensitive capabilities and resources.
•  Use role-based access control (RBAC) to limit access to critical API endpoints and container resource actions like `get`, `list`, `watch`, or `secrets.`
•  Use multi-factor authentication (MFA) for accessing container environments.

3. Network Security

•  Isolate containers using network segmentation (e.g., Docker network policies).
•  Protect public-facing services by filtering traffic at various ports and protocols.
•  Use encrypted communication (e.g., TLS) for data in transit.
•  Use Layer 7 controls with a service mesh and deep packet inspection to enforce HTTP/HTTPS policies.
• Restrict Layer 3 and 4 traffic using control IP-based and port-based access to limit access.
• Certify that the chosen Container Network Interface (CNI) plugin supports Kubernetes Network Policies.
• Apply ingress and egress network policies to all workloads, with default policies in place that deny all traffic.
• Make sure critical components (Kubernetes API, Kubelet API, etc.) are not exposed publicly.
• Encrypt traffic and use Mutual TLS (mTLS) to authenticate workload communication within clusters.

4. Runtime Security

•  Monitor container runtime behavior for suspicious activity.
•  Limit container access to host resources by using Linux security modules.
•  Implement resource limits (CPU, memory) to prevent denial-of-service attacks.
• Restrict runtime API and daemon access to prevent tampering with live containers.
•  Log and audit all container activities in real-time.

5. Vulnerability and Patch Management

• Regularly scan containers and host systems for vulnerabilities.
• Scan configuration files for compliance in your continuous integration pipeline, and incorporate automated checks for security misconfiguration.
• Use image signing (Docker Content Trust) to verify the integrity of the container images.
• Perform static code analysis to identify vulnerabilities in an application code and its dependencies.

6. Secrets Management

•  Store sensitive data (API keys, passwords) in secret management tools.
•  Avoid hard-coding secrets in container images or environment variables.
• Conduct periodic audits and review who has access to Secrets API and rotate encryption keys.
• Encrypt data at rest by configuring the Kubernetes API server to encrypt secret data in etcd, for an additional layer of protection.
• Configure tokens with shorter expiration periods to reduce the impact of a token being compromised.

7. Orchestration Security

•  Secure container orchestrators (e.g., Docker) with strong access controls.
•  Enable role-based access control (RBAC) and ensure the least privilege for users and service accounts.
• Implement version control (such as Git) for orchestrator service definitions and configurations.
•  Enable logging for all API requests to the orchestrator control plane (for instance, audit logs in Kubernetes)

8. Secure Configuration

•  Disable unnecessary services or ports in containers.
•  Use read-only file systems for containers that don’t require write access.
•  Ensure containers are stateless and immutable whenever possible.

9. Backup and Disaster Recovery

•  Regularly back up container configurations and application data.
• Ensure backups are consistent by leveraging etcd snapshot save commands to take a point-in-time backup.
• Perform disaster simulations where you intentionally fail a cluster component and validate that the restore process works as expected.

10. Compliance and Auditing

•  Ensure compliance with industry security standards (e.g., GDPR, PCI-DSS).
•  Regularly audit container security policies, logs, and access control configurations.
•  Conduct regular security penetration tests on container environments.

Container Security Best Practices

Although we have given you a container security checklist, here are some container security best practices that strengthen your containerized environments:

1. Use trusted base images: The foundation of your container is built on the images. So make sure to get them from a reputable source. Also, opt for an automated image scanning and regular patching tool. Use tools that integrate directly into your CI/CD pipeline to check base images as they move through each stage.
2. Implement least privilege: Keep container privileges on a leash. Avoid running containers as root and restrict access to system resources to stay ahead of potential threat vectors. Use CIS benchmarks to harden the host OS by ensuring minimal services are running and consider tools like SentinelOne to reduce attack surface at the system call level. This is important as containers share the host kernel.
3. Secure Infrastructure as Code (IaC): To prevent risky configurations from reaching production, you can use IaC templates like Kubernetes manifests that scan for policy violations and misconfigurations (such as overly permissive IAM roles or exposed ports) before deployment.
4. Cloud configuration hardening: Ensure cloud resource isolation through VPCs and private networks, and harden cloud services using least-privilege access control. Implement continuous monitoring for cloud misconfigurations (like open S3 buckets or exposed management interfaces).
5. Reduce external vulnerabilities: Vulnerabilities in third-party dependencies (mostly found during builds) can introduce weaknesses in your applications. You can automate dependency scanning for known CVEs in both OS and application dependencies. Regularly update libraries and packages.
6. Orchestrator and runtime benchmark controls:  Use orchestrator security controls such as Kubernetes admission controllers to enforce security policies before deployment. Implement runtime benchmark checks (e.g., Kubernetes CIS benchmarks) to regularly audit both orchestrators and running containers.
7. Network segmentation: Create and apply policies to control container traffic and downsize the attack surface. Micro-segmentation of containerized workloads limits the impact of a breach and improves network security.
8. Resource limiting: By applying resource limits to each container’s CPU, memory, and storage, you can prevent any container from exhausting system resources. If system resources are used up, you might face problems with service conditions and other operational issues.
9. Monitor and log activity: You need to respond to security threats in real-time. Get tools that provide visibility into container behavior, allowing you to swiftly identify and mitigate threats.
10. Secure CI/CD pipeline: Ensure your CI/CD pipeline is secure by incorporating security checks at every stage of the container lifecycle, from code commit to deployment. This helps prevent vulnerabilities from being introduced during the development process.
11. Automate security updates: Use automation tools to apply security patches and updates to containers and orchestrators without causing downtime.
12. Compliance and policy enforcement: Audit containers regularly to comply with organizational and regulatory policies. Use policy enforcement tools to apply security policies across environments, and maintain consistent security standards and compliance.

Common Container Security Mistakes to Avoid

In February 2019, the Docker team publicly announced the CVE-2019-5736 vulnerability. Because of this weakness, attackers could overwrite the host’s binary, gain access to the host system, and execute commands as root within a container.

Several organizations, including AWS, RedHat, and Microsoft Azure, also found this vulnerability and applied patches to their products.

In 2021, the CVE-2021-3490 vulnerability exploited a flaw in the Linux kernel related to the extended Berkeley Packet Filter (eBPF).

This weakness allowed attackers to execute arbitrary code on the host from within compromised containers that had access to eBPF through Kubernetes’ default seccomp profiles. These profiles did not restrict the required syscalls, leaving certain setups exposed.

These incidents stand to show that one small oversight in your container security can compromise the integrity of your applications and expose your environment to risks.

Some other common container security mistakes to look out for are:

• Assuming public images are secure can lead to compromised deployments. Never trust external images without a thorough review by experienced developers.
• Exposing containers to too many open channels increases the attack surface. Avoid leaving containers exposed with root permissions, and review network interactions for potential weak points.
• Failing to vet and scan code libraries for vulnerabilities before integrating them into containers
• Not keeping accurate records of logging can make it hard to spot security issues quickly.
• Ignoring CI/CD pipeline security, such as skipping security checks during build and deployment, can introduce vulnerabilities early in development.

SentinelOne Cloud Workload Security for Containers

You need a unified strategy across all nodes to effectively secure all your containerized environments. Q2 is a leading financial service provider to over 1200 banks, unions, and financial institutions. With over 22 million end users and 65,000 containers in the public cloud, Q2 has deployed SentinalOne’s Cloud Workload Security for Containers across all its environments. And like Q2, you too can avail of several features and benefits of this solution, be on top of any anomalies, and maintain a strong security posture.

Key Features and Benefits

• Comprehensive Hybrid Cloud Workload Protection across multi-cloud environments, including AWS, Azure, GCP, and on-premises data centers
• Blocks ransomware, zero-day exploits, crypto miners, and fileless attack
• eBPF-based Agent Architecture delivers real-time visibility at the operating system’s process level, offering deep telemetry without relying on kernel modules
• Static AI Engine that analyzes file architectures by leveraging a dataset of over 500 million malware signatures
• Behavioral AI Engine that uses temporal analysis, evaluating patterns over time to detect malicious behaviors that may evade static detection
• Real-time detection of machine-speed attacks across servers VMS, containers, and Kubernetes
• Automated recovery, for maximum workload availability
• Accelerate investigations and IR, power threat hunts
• Workload Flight Data RecorderTM.
• Accelerate innovation with runtime security that does not get in the way.
• No kernel dependencies. Low CPU and memory overhead.

• eBPF architecture, for stability and performance
• Supports Docker, containers, and cri-o runtimes
• Auto-scaling protection
• Real-time CWPP
• Supports self-managed and managed K8s services
• Supports 14 leading Linux distributions, including Amazon Linux 2023
• Integration with Snyk (purchased separately)

In addition, SentinelOne’s Cloud-Native Application Protection Platform (CNAPP) helps you enhance container security with features like Kubernetes Security Posture Management (KSPM) and Cloud Security Posture Management (CSPM), ensuring your cloud-native applications stay compliant and secure.

Book your demo now!

FAQs

1. How do you ensure container security?

To ensure container security, you need to take a broad approach that covers many layers. start by:

• Using trusted base images and scanning them frequently for vulnerabilities, keeping the images minimal to reduce the attack surface.
• Apply the principle of least privilege by restricting containers to only the permissions they need and never running them as root.
• Continuously monitor container activity in real-time to detect suspicious behavior, and perform vulnerability scans at every stage, from build to runtime.
• Finally, ensure your host and orchestrator are properly hardened with security patches and network policies to limit container communication and reduce potential threats.

2. What are the core elements of the Container Security Initiative?

The Container Security Initiative (CSI) has seven main parts. These include:

1. Scanning images
2. Securing runtime
3. Controlling access
4. Protecting networks
5. Managing compliance
6. Watching
7. Responding to incidents.

3. Which tool is used for container security?

SentinelOne Singularity Cloud Workload Security (CWS) platform plays a big role in container security. It guards containerized apps throughout their life. The platform makes runtime protection automatic, handles vulnerabilities, and enforces compliance. It works with Kubernetes and other systems to see and secure containers in real-time, both in public and private clouds.

4. What are the steps involved in the container security life cycle?

The container security lifecycle has five main steps:

1. Image Security: Begin with safe checked images and check them often to find weak spots.
2. Build Security: Make sure the container build process follows safe rules and methods.
3. Deployment Security: Use safety rules, give the least needed rights, and set up safe networks when you roll out containers.
4. Runtime Security: Keep an eye on containers for odd actions, use runtime safety rules, and keep networks separate.
5. Decommissioning: Take containers out of use making sure to wipe out all private data.