Kubernetes (K8s) is an open-source container orchestration platform designed to automate application container deployment, scaling, and running.
Containers are isolated software packages that are lightweight and contain everything required for running an app.
In Kubernetes, a “sidecar” refers to an additional container that runs alongside the main application container in the same pod to enhance its capabilities.
However, cybersecurity researchers at TrendMicro recently discovered that threat actors can leverage the Sidecar Container injection technique to remain stealthily.
Sidecar Container Injection Technique
Sidecar containers help modularize features and functionalities that do not directly relate to the main application logic but which are necessary for efficient operation.
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They have the same lifecycle and a local network with the primary container that follows the single responsibility principle and improves system maintainability.
Here below, we have mentioned the ways to use sidecar containers for logging purposes legitimately:-
- The sidecar container directs application logs to its standard output:
- The sidecar container operates a logging agent to retrieve logs from the application container:
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The Kubernetes threat matrix provides a structured understanding of the TTPs that may be employed by threat actors against Kubernetes installations as inspired by MITRE ATT&CK.
One technique, like MS-TA9011 Sidecar Injection, allows an attacker to inject a malicious sidecar container into a valid pod for unauthorized code execution and hiding operations rather than deploying another pod altogether.
This is related to MITRE’s Deploy Container (T1610) technique, which allows attackers to deploy containers onto systems they have compromised or gained access to.
They can also compromise the behavior of an already installed sidecar container, install malware, or execute unauthorized binaries such as cryptocurrency miners through API or kubectl tool.
When threatening Kubernetes clusters, this method helps them remain unnoticed within victims’ infrastructures.
Valid sidecar containers increase the difficulty of managing and detecting compromises in a Kubernetes cluster.
It is essential to consider them as any other container and watch out for strange operations. So, it is advisable to introduce a fresh MITRE ATT&CK technique that concentrates on sidecar injection.
Mitigations And Recommendations
Here below we have mentioned all the mitigations provided by the cybersecurity researchers:-
- MS-M9003: Adhere to least-privilege principle
- MS-M9013: Restrict over permissive containers
- MS-M9005.003: Gate images deployed to Kubernetes cluster
Here below we have mentioned all the recommendations:-
- Ensure there’s a valid justification for segregating the containers.
- Aim for concise, modular designs.
- Be mindful of resource boundaries.
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