It’s hard to imagine a modern cloud-native application without Kubernetes. However, it introduces some complex security challenges. Learn how to safeguard your Kubernetes environment from runtime threats and keep your critical workloads out of harm’s way.
Kubernetes is an open-source platform that enables you to automate the deployment, scaling, and management of containerized applications. It’s not wrong to say that Kubernetes has revolutionized the way software are built and deployed. It can orchestrate complex applications across multiple hosts – an ability that has made Kubernetes the standard for cloud-based applications.
With the growing complexity of applications and the distributed and interconnected nature of their components, the attack surfaces grow, too. It becomes important to secure every stage of the SDLC and beyond. That’s where Code to Cloud Security comes in. It’s equally important to secure container images and the Kubernetes control plane against malicious advances. This article will focus on how you can secure Kubernetes at runtime.
What is Kubernetes Runtime Security?
Kubernetes runtime security refers to the practice of securing containerized applications as they run within a Kubernetes cluster. Runtime security ensures that applications are protected against threats that may emerge at a post-deployment stage.
Why is Kubernetes Runtime Security important?
Even though applications undergo robust security checks during the development phases and steps are taken to ensure that container images are secure, vulnerabilities may creep into the production stage. Runtime security for Kubernetes ensures that any such vulnerability is detected and dealt with immediately.
Even rigorously scanned container images can host vulnerabilities that can open ways for exploits during runtime. An infected container might try to gain privilege within the host system, or malicious actors might attempt to make lateral movements between containers and nodes to escalate the damage. Kubernetes runtime security is necessary to tackle these issues.
Key focus areas of Kubernetes runtime security
- Dynamic environment protection: The workload configurations keep changing in Kubernetes. Runtime security must adapt to this dynamism to provide real-time protection.
- Granular network control: Precise control over container communication is necessary to prevent lateral movement of intruders.
- Preventing supply chain attacks: Detecting malicious code before deployment and regular security assessment of images during runtime is one of the goals of Kubernetes runtime security practice.
- Rapid incident response: Runtime security for Kubernetes must enable security teams or business users to launch an incident response quickly in the event of a breach.
Kubernetes Runtime Security Threats
We have already discussed why Kubernetes runtime security is essential to protect an application that is running within a Kubernetes cluster. In this section, we will go through the various threat factors that necessitate runtime security for Kubernetes. The primary security threats faced by applications in their runtime can be divided into five broad categories.
Container-Level Threats
This refers to vulnerabilities that originate from an individual container. These vulnerabilities can compromise the application as well as the host system. There can be various kinds of container-level security issues.
- Image vulnerabilities: Any flaw within the image or the blueprint of the software that can compromise the security of the container or the host system, is an image vulnerability. It can stem from an outdated software package, insecure configurations, or malicious code. Vulnerability scans before deployment usually flush out all image vulnerabilities, but there can be exceptions.
- Privilege escalation: If a malicious actor gains access to a container, they may try to escalate their access by exploiting a vulnerability or taking advantage of unnecessary privileges carried by the container.
- Escape attempts: Containers are designed to keep their contents isolated from the host system – that’s half of the point of using containers. However, hackers can exploit container-level runtime vulnerabilities to attempt an escape from confinement.
- Malicious code injection: Attackers can introduce malicious code into running containers, potentially spreading to other parts of the cluster.
Host-Level Threats
- Host compromise: If the physical or virtual machine hosting the container is compromised, it can give attackers the foothold necessary to target containers.
- Resource abuse: A container intentionally or unintentionally consuming excessive resources can lead to a denial of service. A container might be using too many CPU cycles or it might be sending and receiving too much network traffic. These issues can cause system instability and denial of service. This can be an attack vector in the form of a DDoS attack, data exfiltration, or crypto mining.
Cluster-Level Threats
Cluster-level threats target an entire Kubernetes cluster – all its nodes and the applications contained within – instead of targeting an individual container. An attack as such can potentially disable a cluster, leading to the unavailability of all the apps running within the cluster.
- Unauthorized access: Malicious actors with unauthorized access to the Kubernetes API can abuse the resources.
- API abuse: Legitimate users can misuse the Kubernetes API to cause damage or disruptions.
- Secret theft: Kubernetes Secrets store sensitive information like API keys, passwords, SSH keys, OAuth tokens, etc. Exposition of these secrets can become a major threat.
- Lateral movement: Attackers can move between containers within a cluster thus spreading the infection.
Network-Level Threats
The vulnerabilities in the communication channels between nodes and external systems can compose various kinds of network-level threats.
- Egress traffic: Uncontrolled egress traffic or outbound traffic can cause data leakage and exposition that may lead to unauthorized access or data theft.
- Man-in-the-middle (MitM) attacks: Any unencrypted network communication is susceptible to man-in-the-middle attacks.
- DoS attacks: Hackers can flood a network with fake traffic to disrupt cluster operations.
Other threats
- Supply chain attacks: An attack on the software supply chain can affect multiple containers. This can be done, for example, through malware injection.
- Insider threats: Employees with malicious intent can exploit their privileged access to the cluster to cause damage.
How can Kubernetes Runtime Security Tackle These Challenges?
We have discussed how various threat factors endanger containers, clusters, and even the hosting computers that run Kubernetes clusters. This section will focus on the defense mechanisms you can place to ensure runtime security of Kubernetes.
Network Security
- Network Policies: Well-defined and granular communication rules between pods and services reduces the chance of unauthorized access, eavesdropping, and man-in-the-middle attacks.
- Network-segmentation: You can contain the attack surfaces and limit the potential impact of a breach by isolating workloads into smaller network segments.
- Ingress and Egress Controls: Managing inbound and outbound traffic to and from the cluster helps protect against external threats and data exfiltration.
Threat Detection and Prevention
- Intrusion Detection and Prevention Systems (IDPS): An IDPS can monitor network traffic for suspicious activities, and anomalies, and block threats in real-time.
- Security Information and Event Management (SIEM): This can correlate security events across the cluster to spot potential threats.
Access Control
- Role-Based Access Control (RBAC): Granting access to only the immediately needed resources with time-parameters limits privileged access.
- Secret Management: An encrypted repository of secrets with centralized access controls is necessary for maintaining security and availability.
Resource Protection
- Resource Quotas and Limits: It’s important to set limits on the usage of CPU, memory, and other resources to prevent resource exhaustion and DoS attacks.
- Monitoring: Tracking resource usage continuously and having an alert mechanism helps prevent resource abuse.
Image and Dependency Security
- Image Scanning: Continuously analyzing container images for vulnerabilities prevents deployment of compromised software and also protects against runtime threats.
- Dependency Management: Outdated or compromised dependencies can introduce exploitable security gaps. Ensuring dependencies are up-to-date prevents such issues.
Incident Response
- Incident Response Plan: Having a predefined plan to contain security incidents and eradicate the threats fast can help reduce downtime and address security incidents effectively.
- Security Automation: Automating the routine steps of incident response can reduce response time, remove human error, and augment the remediation process.
5 Best Practices for Implementing Kubernetes Runtime Security
Along with flexibility and scalability, Kubernetes brings some unique security challenges. We have already discussed the key components of Kubernetes security. The following best practices will help you implement robust runtime security for your Kubernetes environment.
1. Enforce the Principle of Least Privilege
Providing minimal necessary access and permissions to users and service accounts forms the core of the least privilege principle. The best way of implementing this is by adopting a zero-trust architecture that abides by a simple motto: never trust, always verify. This introduces verifications across the board whether you are inside or outside the company network.
2. Focus on Image Security
The health of container images and dependencies must be monitored at all times. Regular vulnerability scanning with a robust remediation cycle is necessary. Using immutable container images to prevent runtime modifications is a good idea.
3. Use Runtime Application Self-Protection (RASP)
RASP provides deep visibility into application behavior in real time. It can detect anomalies and take necessary steps to counter the threat elements by blocking a malicious input or ending the session.
RASP is capable of distinguishing between legitimate and malicious activities, so false positives are reduced. Having an RASP in place can be of great benefit.
4. Strong Network Security Measures
Steps like network segmentation, implementation of Ingress and Egress controls, and encryption of network traffic can be crucial for safeguarding network communication.
5. Build a Culture of Security
Embed security into the SDLC with reliable CI/CD integration. This will create a steady cycle of vulnerability assessments. Providing role-based training to employees is just as necessary as conducting regular internal and external audits to measure security readiness. These practices translate into better runtime security.
Kubernetes Runtime Security Tools
There are a number of different tools, both commercial and open-source, that can help you implement runtime security for your Kubernetes environment. We’ll discuss a few of such tools in this section.
1. SentinelOne
SentinelOne has a comprehensive cloud security platform named Singularity. Kubernetes Sentinel is a component of that platform. It replaces pre-production container scans with runtime vigilance for containers. This is one of the best options for automating Kubernetes runtime security.
2. Falco
Falco is an open-source tool that enables the detection of anomalies in containers and hosts. It monitors runtime Kubernetes and raises alerts once it spots anomalous behavior.
3. Kube-hunter
Another open-source tool, Kube-hunter is specifically designed to identify vulnerabilities in the cluster configuration.
4. Kube-bench
This tool checks your Kubernetes cluster against security best practices standardized based on the CIS Kubernetes Benchmark.
Apart from these, there are popular commercial tools like Armo, Palo Alto Networks, etc. that can solve your Kubernetes-related security issues.
Kubernetes Runtime Security with SentinelOne
SentinelOne is focused on providing a truly comprehensive cloud-native security platform to its clients. Kubernetes runtime security and container security in general form a very important part of that agenda.
SentinelOne has a dedicated Kubernetes agent that performs real-time monitoring on the runtime Kubernetes clusters. With continuous vulnerability analysis, SentinelOne ensures that your application’s security posture is in good shape in production. Securing Kubernetes clusters plays an important part in application security, and SentinelOne does it right. Singularity Cloud Workload Security by SentinelOne protects containerized workloads from runtime threats like zero-days, ransomware, and more.
SentinelOne Singularity Data Lake provides security analysts the visibility needed to investigate incidents, slash response time, and inform threat hunting.
Key features of the Kubernetes Sentinel Agent
- Supports 14 leading Linux distributions, including Amazon Linux 2023
- Snyk integration (must be purchased separately)
- Supports Docker, containers, cri-o runtimes
- No kernel models are needed, auto-scaling protection, and real-time CWPP
- Self-managed and managed K8s services
- eBPF architecture for stability and performance
- Accelerates investigations and IR (Incident Response) and powers threat hunts with Workload Flight Data Recorder™
Overall business benefits of adopting SentinelOne for Kubernetes security
- Streamlined security operations reduce business downtime
- Optimized resource utilization
- Helps meet industry regulations and compliance requirements
A quick recap
In this article, we explored the critical nature of Kubernetes runtime security.
- We discussed threats that can endanger containerized environments, from image vulnerabilities to network-level attacks.
- We discussed how Kubernetes runtime security can tackle these threat factors.
- We discussed the essential best practices like implementation of strong access controls, robust network policies and building a culture of security.
- We talked about continuous monitoring and runtime alert management with the help of SentinelOne.
Conclusion
Kubernetes clusters form the core of most of the modern applications that use containerization. Malicious actors often target containers to gain unauthorized access and move laterally across the clusters. Kubernetes runtime security ensures that container images are free of security vulnerabilities, containers are immutable, and no runtime security threats or runtime security risks are looming over the applications.
A multi-faceted approach to Kubernetes runtime security includes network security, access monitoring and security controls, image security, etc. The use of a high-quality RASP mechanism makes things easier for security professionals. Finally, a tool like SentinelOne takes the stress away from container security and cloud security as a whole.