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  • Writer's pictureNexix Security Labs

Docker Security: Challenges And Best Practice

Docker containers have transformed application deployment and management. The technology provides various advantages, including higher efficiency, ease of use, and scalability. However, like with any technology, there are potential security issues that must be considered. In this post, we will look at the security issues connected with Docker containers and how to safeguard them.

Why Docker Security is important ?

In today's world, virtual machines are one of the most common deployment models for cloud and IT infrastructure. However, it is important to know how to harden these environments to protect against threats. In particular, it is important to understand how Docker differs from traditional VM deployments and how you can use Docker without compromising on security by using containers that run within your existing network infrastructure.

Container security is often underestimated, but it's a real concern for your business. Dangers include the fact that containers aren't often able to detect intrusions, and they act as a single point of failure.

  • Containers: Docker containers are designed to enforce security. A single compromised Docker container can threaten all other containers as well as the underlying host, underscoring the importance of securing Docker. Regardless of the size of organisation, individual microservices will be hosted on different containers following immutable infrastructure. Monitoring these containers on different instances for security incidents is complex, which is why we recommend using Kubernetes as your platform-as-a-service (PaaS).

  • Host Server: Security is a big concern. You can either use a bare metal or an on-premise VM or a cloud instance. While using additional layers for cloud services like AWS ECS, AWS EKS, etc., security will be more difficult to manage.

Vulnerable and Malicious Container Images

Malware, unauthorised access, and network attacks can all be used to target Docker containers. Image vulnerabilities are one type of security issue related with Docker containers. Docker containers are built on top of Docker images, which are snapshots of an application's dependencies. If a vulnerability exists inside the image's components, an attacker can exploit it, resulting in a security breach.

How to mitigate

  1. Avoid untested or untrusted builds and apply the latest security updates to minimise the risk of vulnerabilities being introduced by your software.

  2. Docker Certified Containers are a safe option to use. These certified containers are not only validated by Docker but also have been built to meet best practices in security, performance and reliability. Docker Store packages are another great way to get started with Docker.

  3. You can also use a trusted third-party registry with built-in scanning.

Privilege escalation in a host using Docker

Container escalation is another security vulnerability connected with Docker containers. Docker containers run with limited privileges by default, but if an attacker can elevate their privileges within the container, they can obtain access to the host system and additional containers, resulting in a much wider security compromise.

How to mitigate

  1. In the rootless mode, Docker runs in the user namespace. 'User Namespace' is a Linux feature that allows you to separate users and groups between a user's host system and the containers running inside it. This separation allows for better isolation of processes, which also means fine-grained access control without sacrificing security.

Unrestricted Access

A possible security issue connected with Docker containers is network assaults. Containers are vulnerable to the same types of network-based assaults as other technologies since they are often implemented in network environments. An attacker, for example, could target network protocols used by Docker containers, such as the Docker API, to obtain unwanted access or steal data. Finally, a misconfigured Docker daemon may pose a security concern. The Docker daemon is in charge of maintaining containers on a host, and if it is incorrectly configured, an attacker may acquire unauthorised access to the host system and containers.

How to mitigate

  1. Avoid untested or untrusted builds to prevent the introduction of vulnerabilities and malicious code.

  2. Apply the principle of least privilege and eliminate root access where possible. For instance, you can enable the user namespace feature to provide separate user accounts for isolated containers to restrict movement between containers.

Securing containers

To secure Docker containers and limit the chance of a security incident, numerous best practices can be followed.

To begin, only use Docker images from reputable sources, such as official repositories, and check for security upgrades on a regular basis. The Docker environment, including the Docker engine, images, and other components, should be kept up to date to ensure that vulnerabilities are patched and security concerns are reduced.

It is also critical to use the most recent Docker version, which includes the most recent security improvements and bug patches. Furthermore, limiting the privileges of Docker containers by using the "—privileged" flag only when necessary and running containers as a non-root user can help to lessen the chance of a security breach. The Docker environment can be made more secure by separating containers by deploying them on different networks, employing network security groups, or using firewalls.

Virtual Private Networks (VPNs) and other encrypted networks should be used to safeguard communication between containers, and routine monitoring of container activity, including malware, network attacks, and unwanted access, is advised.


Containers are a great way to introduce microservices across different IT environments. However, containers also increase the attack surface and risks because containerization of software also adds extra layers of abstraction and complexity which can increase docker vulnerabilities in the container environment. Therefore, we believe that the key challenge for security is not just to understand how containers work, but also to discover ways to effectively protect these systems against attacks.

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