What is container security?

Container security aims to both enhance protection measures and minimize security risks.

First, let’s be clear about what we’re discussing because “container security” can have multiple meanings. Containers are self-contained software units that bundle application code with all necessary libraries and dependencies. They enable code to run in any computing environment, including desktop, traditional IT and cloud infrastructure. The security challenges that we’re describing here focus on those containers that hold and safeguard data.

Data is now the lifeblood of commerce and communication. The modern world would grind to a halt without data, which is why information must be protected at all costs. Deception and crime are still permanent aspects of the human condition. Today’s cybercriminal has the same motivations as yesterday’s thief, only outfitted with the tools and know-how to exploit security vulnerabilities.

To fully protect data, we need to understand containers. Plus, we need to be sure that we comprehend the significance of apps because that’s what containers hold—apps performing a multitude of actions on a company or individual’s data.

How many apps? It’s a tricky number to tease out, but by April 2025, Google Play and the Apple App Store each offered around 2 million distinct apps. Whether these apps are being used by an organization or an individual, security vulnerabilities almost certainly occur based on the transfer of data from the app user to the app itself.

This transfer ranges from an individual providing personal financial data to play on a gaming app to a company supplying sensitive data and proprietary information to an accounting app. If such information is stolen (through malware or other types of cyberthreats) or exposed, it might lead to public relations nightmares, loss of competitive edge and security breaches. It might even lead to the theft of millions or even billions of dollars’ worth of customer data.

So, at all levels, there are massive amounts of private information being shared with and through apps. The stakes are substantial, which is why maintaining a strong container security posture is a vitally important part of cybersecurity.

In a software development context, container technologies hold everything needed for applications to run. The container packages it all up as a self-contained entity that’s ready to go and capable of being run consistently on various types of environments. All the files required to run the app are here:

• Application code: The application code includes all executable files for the application, such as the source code and compiled binary code.

• Runtime environment: The container runtime environment contains the frameworks, libraries and tools that are needed to execute the application’s code.

• System libraries: System libraries are shared resources that offer common functions such as graphics libraries, networking libraries and file input/output transport node.

• System tools: Each app requires specific utilities and tools to help it run its functions properly.

• Configuration files: Configuration files establish the way that the app behaves and which settings apply to it.

• Dependencies: Dependencies are the externally located frameworks, components and libraries that the app must be able to access in order to perform as expected.

• Environment variables: Development, testing and production environments can be altered per the runtime activity exhibited by the container. Variables within containerized environments help control those settings.

• Operating system kernel: Containers don’t require a full operating system (OS). Instead, they use a type of operating system virtualization that leverages features of the OS kernel.

• Security settings: These settings let the user customize the security measures in place to regulate variables such as access controls, capabilities and resource limits.

Container images are static and unchanging files that hold executable code and operate in isolation on IT infrastructure. The container image holds the components needed to create a container on an operating system. Container images are aggregated with different layers and function like templates.

Container images are the default format for delivering applications in cloud-native environments, and it's where container security begins. The base image is critical for security, as it's the foundation for all derivative images. Container security begins with using trusted sources, ensuring that the image comes from a reputable organization, is hosted on a reliable registry and includes accessible source code for all components.

It's imperative to employ proactive vulnerability management throughout the lifecycle, even when starting with a trusted base image. Regularly scan all container images by using an image scanner, either integrated into the registry or provided as a separate tool. Also, identify container images that violate policies or best practices, commonly referred to as container misconfigurations.

The software development lifecycle (SDLC) governs the “seasons” of the life of a piece of software and its working existence. The seven stages outlined here are all necessary and should be performed sequentially.

Numerous key technologies work hand-in-glove with these development stages, and these solutions (and the security measures they provide) are also discussed at the point at which they should occur in the SDLC.

The initial stage is defining all aspects of the project. That means first to outline the scope of the project, as well as its expected goals and the resources that are available for the effort. But it typically also includes other activities such as cost-benefit analysis, feasibility studies and scheduling.

It’s suggested that the following two related technologies are discussed during the planning stage, as both can be implemented during any part of the SDLC:

• CI/CD pipeline: The continuous integration/continuous deployment (CI/CD) pipeline is a DevOps workflow where containerized apps gain speed and streamlining by using automated security checks. Through automated and continuous security monitoring, issues can be flagged for remediation efforts so repairs can occur before further ramifications ensue. The pipeline can further be strengthened by implementing shift-left, an approach that integrates security measures earlier in the DevOps process. Using containers together with a CI/CD pipeline helps the overall integration of security practices into workflows used by DevSecOps teams.

• Supply chains: Supply chains represent another example of a related technology that’s been thoroughly interwoven with container security elements. Security teams working to strengthen supply chain container security engage in regular scanning of container images and related components. Doing so helps handle new cyberthreats and known vulnerabilities.

The next stage involves drilling down further into the project’s needs, as seen through the lens of the needs of stakeholders and users. All the various requirements that apply to the project need to be collected, analyzed and managed.

At this stage, the designer usually takes the spotlight because it’s time to funnel all that gathered information about requirements into a workable software design. This blueprint describes the architecture needed, the data structures required and the user interface that should be adopted.

There are four related technologies that ideally should be addressed during the design stage, if they are to be used.

• Cloud: The widespread adoption of containers has coincided with the similarly broad embrace of cloud computing. Containers are now being used within the cloud in great numbers to create cloud-native applications. The responsibility for protecting cloud-based information assets falls to cloud service providers such as IBM Cloud, Google Cloud, Microsoft Azure and Amazon Web Services (AWS). Establishing cloud security involves enacting security measures that foster data protection, infrastructure security and identity management. Workloads moved to the cloud deal with the same basic security issues; image repositories still need routine scanning to ensure their viability, even if stored in cloud environments. Cloud implementation should ideally begin during the design stage of the SDLC, as it significantly impacts architecture and resource planning—both of which must be addressed before development starts.

• Linux: Linux is an instrumental part of container security. The open source platform supplies the basic building blocks used in container security and necessary security features like firewalls. Linux namespaces are places to effectively isolate running containers within their environment and minimize their access to resources while maintaining otherwise consistent operation. Linux containers fully leverage the capabilities of the Linux kernel by using various methods to restrict and isolate containerized workloads. Linux is where key program details are finalized and actual coding begins. As such, it can take place during the design stage or later implementation.

• Microservices: As with Linux, microservices use containers to impose isolation on each microservice and give it its own “sandbox” environment apart from the host OS and other services. This reduces the attack surface and improves its defensive capabilities, in addition to giving microservice containers extra scalability. As with other container-security best practices, microservices employ the principle of least privilege, by which a container is only given the absolute minimum necessary privileges so it can execute its function as intended but not exceed its ability to access resources or impinge on other containers. Optimally, microservices should be used during the design stage because that’s where monolithic apps are broken down into smaller services that can then be deployed independently. However, in some circumstances, microservices can also be used during the deployment stage.

• Virtual machines: Virtual machines (VMs) can provide extra container security because they offer an added layer of isolation. VMs have their own independent OS, lessening the risk of containers becoming contaminated through interaction with other containers, as they don’t have to reach out to a host system for resources. VMs also exhibit a stronger security boundary than containers alone can achieve, which helps reduce the chance that a security breach spreads throughout the file system and negatively affects workflows being processed. The use of virtual machines should occur in the design stage because that is where a system’s architecture and structure are theorized and planned.  

With all the “prep” work accomplished, it’s finally time to build the software by using the design specs provided by the software designer. The developer writes the code, creates application programming interfaces (APIs) and sees that components are integrated as needed.

Although Linux is typically used during the design stage, it’s also used during development because that’s when the software architecture and platform are chosen and where the software coding process begins.

Creating a system of proper testing ensures that the created code performs as expected and remains free of bugs. It’s important to automate policies that flag builds with security issues, particularly as new vulnerabilities are discovered. Patching containers is not as effective as rebuilding them, so security testing should include policies that trigger automated rebuilds. The testing stage can include integration testing, unit testing and system testing.

Presuming all previous steps have been completed, it’s time to publish the software and release it to users. Deployment covers all related tasks necessary for readying the software product for mass distribution, such as packaging and configuring the software.

Kubernetes supports container orchestration efforts and container security by giving it an automated and open source platform for safeguarding containerized apps. Kubernetes environments offer security features such as role-based access control (RBAC), network policies that govern the communication between pods (as Kubernetes refers to containers). They also offer secrets management (which prioritizes the secure storage of sensitive data, such as passwords, API keys, encryption keys and tokens).

Kubernetes security processes apply regular monitoring across Kubernetes clusters in search of possible misconfigurations—any settings that can open the door to security risks and expose vulnerabilities. And while, technically, Kubernetes can be employed during any part of the software’s journey, the acknowledged primary use of Kubernetes is handling the deployment and scaling of containerized apps.

As mentioned earlier, microservices can also be used during the deployment stage.

The last stage of the SDLC process is providing continuing support for the software. This stage can involve generating program enhancements, bug fixes and other types of performance improvements.

There are various routine steps that organizations can take to help underscore the effectiveness of their security policies. Most of them reflect common-sense approaches and use proven vulnerability management principles: