Kubernetes Security: Understanding the Attack Surface

What is Kubernetes Attack Surface?

In cybersecurity, an attack surface consists of the total possible entry points that allow unauthorized access into protected IT environments. It encompasses the entire area susceptible to attacks, including all endpoints and vulnerabilities that attackers can potentially exploit to carry out a cyber attack.

Kubernetes deployment is the process of deploying and managing containerized applications on a Kubernetes cluster. Kubernetes is an open-source container orchestration system that automates the deployment, scaling, and management of containerized applications. It has a unique and complex attack surface consisting of many components not found in traditional environments, such as hundreds of thousands of containers.

The complexity of the Kubernetes architecture and the few built-in security controls it provides create a huge attack surface that makes Kubernetes workloads a prime target, exposing organizations to severe risks. Understanding the Kubernetes attack surface is crucial to applying proper security controls and managing risks across this highly dynamic ecosystem.

Kubernetes Attack Vectors

An attack vector is a method or technique that a hacker or attacker uses to gain access to a computer system, network, or web application with the intention of causing harm or stealing sensitive information. Here are the three main Kubernetes attack vectors:

External Attackers

External attackers may try to gain unauthorized access to a Kubernetes cluster by exploiting vulnerabilities in the Kubernetes software or misconfigurations in the cluster. They may also try to launch a denial-of-service attack or steal sensitive data stored in the cluster.

Malicious Containers

Attackers may try to deploy malicious containers to a Kubernetes cluster. These containers may contain malware or backdoors that can be used to steal sensitive information or launch further attacks.

Compromised or Malicious Users

Kubernetes clusters typically have multiple users, including developers, system administrators, and other stakeholders. If a user’s account is compromised or if a user is acting maliciously, they may be able to steal sensitive data or launch attacks on the cluster.

Understanding the Kubernetes Attack Surface

Exposed Sensitive Interfaces

Exposed sensitive interfaces are parts of the Kubernetes attack surface that can be accessed from external networks and can be used to gain unauthorized access to a cluster or steal sensitive data. Here are a few examples of exposed sensitive interfaces in the Kubernetes attack surface:

• API Server: The Kubernetes API server is the main interface for managing a Kubernetes cluster. It allows users to create, update, and delete resources in the cluster. If the API server is exposed to external networks, attackers may be able to use it to steal sensitive data or launch attacks on the cluster.
• Kubernetes Dashboard: The Kubernetes dashboard is a web-based interface that provides an overview of the resources in a cluster. It can be used to create, update, and delete resources, and can also be used to view sensitive data such as secrets and configmaps. If the dashboard is exposed to external networks, attackers may be able to use it to steal sensitive data or launch attacks on the cluster.
• Kubernetes Nodes: Kubernetes nodes are the worker machines in a cluster that run the containerized applications. If a node is exposed to external networks, attackers may be able to use it to steal sensitive data or launch attacks on the cluster.
• Kubernetes Service: Kubernetes services expose network endpoints for the pods and can be used to balance the load of the incoming traffic. If a service is exposed to external networks, attackers may be able to use it to steal sensitive data or launch attacks on the cluster.

Sidecar Injection

A sidecar container is a container that runs alongside the main container in a pod, providing additional functionality such as logging, monitoring, or security. Sidecar containers are often used in Kubernetes to provide functionality that is not directly related to the main application. For example, a sidecar container could be used to collect and forward logs from the main container, or to automatically rotate secrets used by the main container.

A sidecar injection attack is when an attacker modifies a pod in a Kubernetes cluster to include a malicious sidecar container that can be used to steal sensitive data or launch further attacks. This can happen if an attacker is able to gain access to the Kubernetes API server, or if they are able to exploit a vulnerability in the pod’s configuration.

CoreDNS Poisoning

CoreDNS is a DNS server that is used in Kubernetes clusters to provide service discovery and name resolution. CoreDNS Poisoning is an attack where an attacker alters the DNS information stored in a Kubernetes cluster in order to redirect traffic to malicious domains or IP addresses. This can happen if an attacker is able to gain access to the Kubernetes API server, or if they are able to exploit a vulnerability in the CoreDNS configuration.

Once the attacker has poisoned the CoreDNS server, they can use it to redirect traffic to malicious domains or IP addresses. This can be used to steal sensitive data, launch further attacks, or perform man-in-the-middle attacks to intercept traffic.

Kubernetes Indicators of Compromise

Kubernetes Indicators of Compromise (IoCs) are signs or patterns that indicate that a Kubernetes cluster or its resources have been compromised. These indicators can help identify a security incident and can be used to determine the scope and impact of an attack. Here are a few examples of Kubernetes IoCs:

• Unexpected changes in resources: Unusual modifications to pods, services, secrets, or configmaps are an indication that an attacker may have gained access to the Kubernetes API server and modified resources in the cluster.
• Unusual network connections: Unexpected connections to external IP addresses or domains, or connections to internal resources that are not part of the normal traffic pattern, are an indication of a potential attack.
• Unusual processes running: The presence of unusual or unknown processes running on a Kubernetes node or pod is an indication that an attacker may have deployed a malicious container.
• Abnormal resource usage: Unusual spikes in resource usage, such as CPU or memory usage, can indicate that an attacker is using a resource-intensive attack, such as a denial-of-service attack.
• Unusual log entries: Unexpected error messages or log entries can indicate that an attacker is attempting to exploit a vulnerability in the Kubernetes software.

It is important to monitor and collect these indicators from different sources, such as Kubernetes APIs, nodes, pods, services, and network traffic. Looking for these indicators can help detect and respond to security incidents early on and take appropriate action to mitigate the attack.

Conclusion

In conclusion, the Kubernetes attack surface is highly dynamic and complex, making it a prime target for attacks. The main attack vectors include external attackers that attempt to exploit security weaknesses like exposed dashboards, malicious containers, and compromised or malicious users. It is critical to understand the Kubernetes attack surface and monitor for IoC to properly protect Kubernetes workloads and prevent attacks from occurring.

Author Bio: Gilad David Maayan

Gilad David Maayan is a technology writer who has worked with over 150 technology companies including SAP, Imperva, Samsung NEXT, NetApp and Check Point, producing technical and thought leadership content that elucidates technical solutions for developers and IT leadership. Today he heads Agile SEO, the leading marketing agency in the technology industry.
LinkedIn: https://www.linkedin.com/in/giladdavidmaayan/

Read Next: Security Service Edge vs. SASE: What Is the Difference?