Containers are lightweight, isolated environments that share the host OS's kernel, supporting faster startup and lower overhead. Virtual machines, on the other hand, emulate entire physical systems, each running its full operating system, which makes them more resource-intensive.
Thanks to VM technology and containers today, you can isolate applications throughout your cloud infrastructure for improved security. Learn the distinctions between containers and VMs and examine their roles in resource isolation, efficiency, and security within digital environments.
Before diving into containers and VMS, here’s an overview of how these choices can determine your infrastructure:
| Feature | Containers | VMs |
|---|---|---|
| OS virtualization | Share host OS kernel | Full OS virtualization (guest OS per VM) |
| Resource usage | Lightweight (minimal overhead) | High resource consumption |
| Startup time | Rapid (seconds) | Slower (full OS boot required) |
| Isolation | Lighter isolation | Strong isolation |
| Use case | Microservices, CI/CD pipelines | Legacy apps, multi-OS environments |
What are containers?
Security containers are isolated environments that run applications securely while minimizing risk. These containers encapsulate apps and their dependencies to function consistently throughout the different cloud environments.
For production environments, container orchestration platforms like Kubernetes are essential for managing, scaling, and securing containerized applications. Kubernetes provides features such as automatic load balancing, rolling updates, and self-healing capabilities.
Security engineers should focus on implementing container-specific security measures, such as:
Using trusted base images and maintaining a private image registry
Implementing vulnerability scanning in CI/CD pipelines
Applying runtime security policies using tools like Falco or Aqua Security
Implementing network segmentation using Kubernetes Network Policies
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This cheat sheet goes beyond the no-brainer container security best practices and explores advanced techniques that you can put into action ASAP. Use this cheat sheet as a quick reference to ensure you have the proper benchmarks in place to secure your container environments.
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How containers work
Similar to virtualization, container technology also serves as a method for achieving resource isolation. The key distinction between virtualization and containerization is that containers do not require their own dedicated OS. Instead, one operating system hosts multiple individual containers, saving physical resources (e.g., RAM, storage, CPU), lowering licensing fees, and reducing other overhead costs.
Figure 1 shows containerization from a bird's-eye view. As you review the diagram, it’s important to examine the container runtime engine role, which runs on the host operating system. Docker serves as the de facto container runtime engine, but many others exist, including CRI-O and rkt.
All container runtimes follow the Open Container Initiative (OCI) governance structure. OCI includes three primary specifications:
Image-spec: Describes the physical structure of container images
Runtime-spec: Describes how containers run in a given runtime
Distribution-spec: Describes API functionality and provides a framework for creating, distributing, and running containers to ensure portability and isolation in containerized apps
What are virtual machines?
Virtual machines use virtualization to achieve resource isolation. In virtualization, host machines contain separate VMs with individual operating systems and dedicated virtual hardware.
A hypervisor enables this logical separation by managing physical resources and allocating them to VMs as needed. As illustrated below, hypervisors play an important role in emulating underlying hardware.
To mitigate hypervisor vulnerabilities, implement the following best practices:
Regularly patch and update hypervisors.
Use hardware-assisted virtualization features (e.g., Intel VT-x, AMD-V).
Implement strong access controls and network segmentation for management interfaces.
Monitor hypervisor logs for suspicious activities using SIEM tools.
How VMs work
There are two primary types of hypervisors:
Embedded/hosted hypervisors: Run as software applications, requiring an underlying guest operating system to operate
Examples: VMware Workstation and Oracle VM VirtualBox
Bare metal hypervisors: Run directly on physical hardware without requiring an operating system; faster and more secure than embedded/hosted hypervisors
Examples: VMware ESX/ESXi, Citrix Hypervisor, Red Hat Virtualization (RHV), Kernel-based virtual machine (KVM), and Microsoft Hyper-V
Hypervisors monitor and control all the resources while managing VMs, making them a frequent target for hackers. The most recent incident was CVE-2021-21974, a ransomware attack on the VMware ESXi hypervisor. It's important to have a strong understanding of existing vulnerabilities—as well as security measures—to monitor the server environment.
What are the similarities between virtualization and containerization?
Virtualization and containerization abstract computing resources from the hardware layer (Figure 3). This enables multiple virtual environments and containers to run in parallel on a single host machine, reducing businesses' need to purchase new hardware for each application. This resource separation is a key building block in modern cloud computing.
All existing cloud providers—including AWS, Azure, and Google—use virtualization and containerization under the hood to maximize resource utilization, reduce ownership costs, and offer more flexibility.
Key differences between containers and VMs
Virtualization and containerization can coexist and outperform each other depending on the scenario, so knowing each approach's strengths is important. Reference the chart below for a side-by-side comparison:
| Category | Virtual machines | Containers |
|---|---|---|
| Isolation levels and security | VMs offer full isolation, which limits damage caused by a breach. Still, the hypervisor is a common target for attackers. Implement virtual firewalls and micro-segmentation. | Containers leverage flexible isolation through network configurations like bridge, host, and none. Adopting host networks minimizes security and none networks offer full isolation. Use runtime security tools (e.g., Falco, Sysdig Secure). |
| Performance overhead and efficiency | Your team needs more resources for VMs since they run on full OS instances. VMs can outperform containers, like memory and bandwidth tests, in some cases. Use dynamic resource allocation (e.g., memory ballooning). | Containers utilize OS kernels. This makes them more resource-efficient. The containers have quicker start times and are optimized for improved disk and memory usage. Set resource limits/requests in Kubernetes. |
| Scalability and resource utilization | Each VM uses significant resources because of the OS overhead. Due to the higher consumption, your team may find it more difficult to scale. Use cloud provider auto-scaling groups. | Containers only need application dependencies for lightweight infrastructure and scalability. Implement auto-scaling using Kubernetes Horizontal Pod Autoscale. |
| Deployment, orchestration, and management | VMs follow traditional configuration management. This makes them more appropriate for legacy applications. Use infrastructure-as-code tools like Terraform. | Containers can take advantage of automation through tools like Kubernetes and Docker Swarm. This makes them helpful for microservices. Implement GitOps practices using tools like ArgoCD or Flux. |
Below, we dig deeper into each category:
1. Isolation levels and security
Containers and VMs both provide isolation and security but on different levels. VMs offer full isolation, yet attackers can still compromise them. Their advantage is that once compromised, VMs remain completely isolated from neighboring VMs.
Still, attackers more commonly target the hypervisor in virtualization because it gives them full control of the VMs the hypervisor manages. Containers offer more flexible isolation.
For example, Docker containers provide different network configurations depending on the required isolation level:
Bridge network: Docker's internal IP address management (IPAM) assigns a subnet, allowing communication between all containers assigned to that bridge network via their own IP addresses.
Host network: All containers share the host operating system's network namespace. This reduces security because it eliminates network isolation.
None network: Contrary to the host network, containers here will not attach to any networks, meaning they cannot communicate and, in turn, provide full isolation.
With containers, the processes, file system, and resources (CPU, RAM, disk) also have flexible isolation, making containers more vulnerable. However, with good security measures and scanning tools like Wiz and Kubescape, you can secure the environment.
2. Performance overhead and efficiency
Containers require fewer resources than VMs because they share the physical machine hardware and OS kernel with other containers. This improves performance and reduces startup time.
Martin Lindström at the Blekinge Institute of Technology conducted a comprehensive study highlighting that, generally, container-based systems outperform virtual machines in disk performance and memory usage. However, VMs outperformed containers in specific memory tests like memory bandwidth.
3. Scalability and resource utilization
Each VM requires resources equivalent to a full operating system instance, which increases resource overhead compared to containers.
Containers require only application dependencies, making their resource utilization very efficient. They start almost instantaneously due to their lightweight nature, allowing rapid scaling as application demand changes.
4. Deployment, orchestration, and management
For containers, orchestration tools like Docker Swarm and Kubernetes automate deployment and management, including scaling, service discovery, load balancing, and state management. This automation is essential for complex microservice applications.
VMs follow more traditional configuration management with less automation, making them better suited for running legacy apps.
Kubernetes Security Best Practices [Cheat Sheet]
This 6 page cheat sheet goes beyond the basics and covers security best practices for Kubernetes pods, components, and network security.
Download Cheat Sheet
Choosing between containers and VMs
Despite their popularity, containers will never replace VMs. Teams need both for different requirements. Make sure you know what factors to consider when choosing between the two.
Use cases for containers
Microservice applications: These require ease of scaling and ease of communication between the services, which makes containers an ideal candidate.
DevOps and agile environments: Containers support CI/CD and agile development practices by providing consistent environments—from software development through production.
Highly scalable applications: Containerization makes it comparatively easy to dynamically scale ecosystems based on demand.
Use cases for VMs
Legacy applications: These often require a specific OS or sometimes have complex dependencies that make containerization difficult.
High-security environments: VMs provide strong isolation compared to containers, which makes them ideal for applications with high-security requirements.
Stable workloads: Applications with predictable, stable workloads that do not require frequent scaling can be efficiently deployed on VMs.
Hybrid approaches
There are instances in which using both technologies will provide a versatile, efficient, and secure environment for deploying applications. That's when tools like RancherVM, Red Hat OpenShift® Virtualization, and KubeVirt prove especially helpful as they manage virtual machines and containers.
As seen above, KubeVirt's basic architecture allows users to leverage Kubernetes' powerful orchestration capabilities for both containerized and virtualized workloads, making hybrid environment management easier. With this integration, you can manage containers and VMs side by side using the same set of tools and APIs. This simplifies mixed workload deployment and management in a cloud-native environment.
Security best practices for containers and VMs
The following practices help improve your container and VM security:
Tips for securing containers
Check for secure container images: Verify the origin of container images, scan for vulnerabilities before deployment, and use minimal, trusted base images to reduce risk and improve security.
Use tools like Trivy or Anchore to scan images for vulnerabilities before deployment
Minimize the attack surface: Eliminate unnecessary software, services, and open network ports to minimize potential attack vectors and reduce opportunities for hackers.
Leverage container security tools: Use vulnerability scanners to identify weaknesses, configuration checkers to enforce best practices, and runtime security monitoring tools to detect and respond to threats in real time.
Adopt a solution like Wiz for a holistic and unified cloud security platform that can protect containers.
Practice regular audits: Regularly audit container activities, configurations, and components to detect irregularities, identify security issues, and maintain integrity by monitoring images, runtime settings, and inter-container communications.
Implement strict access controls: Enforce strict access controls on container registries by implementing role-based access control (RBAC) for granular permissions, applying least privilege to limit access, and enabling multi-factor authentication (MFA) to prevent unauthorized access and image tampering.
Set up MFA like Okta Adaptive MFA or Microsoft Entra ID to prevent unauthorized access. Ensure MFA is enforced across all users using sensitive data and systems.
Protect container orchestration: Secure container orchestration by protecting API access, using network policies, checking configurations, and leveraging RBAC for Kubernetes. Do this while implementing AWS’s shared responsibility model, zero-trust IAM, and end-to-end encryption for Amazon ECS.
Tips for securing virtual machines
Encrypt data and control keys: Protect your information through all stages, like at rest in data centers or in transit with encryption. You can consistently rotate keys with customer-managed encryption keys (CMEK) for improved control over security.
Use a key management service like AWS KMS or HashiCorp Vault to manage encryption keys.
Automate patching: Regularly leverage automated patching to keep software and systems up to date, especially as new threats introduce themselves. By automating patches, you can save time and manual labor for more efficient improvements.
Secure access with strong authentication: Use PoLP, MFA, sophisticated passwords, and RBAC to prevent unauthorized access.
Install endpoint protection: Strengthen your security with endpoint detection and response (EDR) tools, SIEM integration, and antivirus tools. These resources help find threats immediately so you can respond quickly.
Leverage unified cloud security platforms like Wiz to automate detection for security threats and vulnerabilities, and prioritize risks with action-oriented recommendations for remediation.
Centralized security logging: Integrate your logs with a unified security platform through automated integration. This helps automate analysis to spot real-time threats throughout your cloud infrastructure.
Containers or VMs: Which will you choose?
The debate between containers and VMs extends beyond technical comparison to a strategic consideration of application deployment and management. Specific project requirements, security considerations, and scalability needs determine the choice between the two technologies.
Whichever you choose, maintaining a strong security posture remains essential.
Your organization should continuously evaluate its deployment strategies for performance and scalability, as well as its ability to withstand emerging security threats. This is where solutions like Wiz come into play, offering comprehensive security and compliance monitoring across both containers and VMs.
Wiz provides deep insights into your deployments' security health, ensuring your infrastructure remains secure and compliant whether you use containers or VMs. See how our industry-leading platform can secure your containers, VMs, and the rest of your cloud infrastructure. Schedule a demo today.
Get the free Advanced Container Security Best Practices [Cheat Sheet] to learn more about container security practices.