Quick Answer
The correct answer is to use minimal base images like Alpine or distroless and to run containers as a non-root user. Minimal images drastically reduce the attack surface by eliminating unnecessary packages, libraries, and utilities that an attacker could exploit, while running as a non-root user enforces the principle of least privilege by ensuring that even if the application is compromised, the attacker cannot gain root-level control over the container or the host. On the CompTIA SecurityX CAS-004 exam, this question tests your understanding of container hardening within the broader domain of secure DevOps practices; a common trap is to focus only on network segmentation or image scanning, forgetting that the image itself and the runtime user context are foundational. A helpful memory tip is “lean and low” — keep the image lean with minimal content and keep the process running with low privileges.
This CAS-004 practice question tests your understanding of scripting, containers and automation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A DevOps engineer is automating the deployment of a web application using containers. Which of the following security practices should be implemented to reduce the attack surface of the containers? (Select TWO.)
Build images with embedded database credentials
Why wrong: Embedding secrets in images is insecure; they should be injected at runtime.
Expose port 22 for SSH debugging
Why wrong: Exposing SSH adds an attack vector and is unnecessary in production.
Grant all Linux capabilities to the container
Why wrong: Granting all capabilities weakens isolation; should drop all unnecessary capabilities.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Run containers as a non-root user
Running containers as a non-root user (option A) is a fundamental security best practice because it limits the privileges available to processes inside the container. If an attacker compromises the application, they will not have root access to the host or the container runtime, reducing the potential for privilege escalation or host-level damage. This aligns with the principle of least privilege, which is critical for container security.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Build images with embedded database credentials
Why it's wrong here
Embedding secrets in images is insecure; they should be injected at runtime.
Expose port 22 for SSH debugging
Why it's wrong here
Exposing SSH adds an attack vector and is unnecessary in production.
Grant all Linux capabilities to the container
Why it's wrong here
Granting all capabilities weakens isolation; should drop all unnecessary capabilities.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CAS-004 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is wrong here
Embedding secrets in images is insecure; they should be injected at runtime.
Why this is wrong here
Exposing SSH adds an attack vector and is unnecessary in production.
Why this is wrong here
Granting all capabilities weakens isolation; should drop all unnecessary capabilities.
Analysis generated from the official CAS-004blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
CompTIA often tests the misconception that containers are inherently secure because they are isolated, but the trap here is that default root execution and bloated base images are common misconfigurations that dramatically increase the attack surface, and candidates may overlook the need to explicitly drop privileges and minimize image content.
Detailed technical explanation
Under the hood, Docker and other container runtimes use Linux kernel features like namespaces and cgroups to isolate processes, but the default user inside a container is root (UID 0) unless explicitly changed. Running as non-root (e.g., USER 1000 in a Dockerfile) ensures that even if a kernel exploit occurs, the attacker's process lacks the privileges to escape the container or modify host-level resources. Minimal base images like Alpine (based on musl libc and BusyBox) or distroless images (from Google) reduce the attack surface by removing unnecessary binaries, libraries, and package managers, making it harder for an attacker to execute post-exploitation tools like netcat or curl.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: Run containers as a non-root user — Running containers as a non-root user (option A) is a fundamental security best practice because it limits the privileges available to processes inside the container. If an attacker compromises the application, they will not have root access to the host or the container runtime, reducing the potential for privilege escalation or host-level damage. This aligns with the principle of least privilege, which is critical for container security.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security audit reveals that Docker containers are built with multiple unnecessary layers and utilities. Which practice reduces the attack surface of the container image?
hardWhy B: Using a minimal base image with only required packages reduces the number of potential vulnerabilities. Multi-stage builds help but don't directly reduce the base image size.
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Last reviewed: Jun 30, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-004 exam.
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