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Application & OT Security · Intermediate

Container Image Hardening

Building container images with minimal contents, non-root users and no secrets to reduce attack surface.

Definition

Practices include using minimal or distroless base images, multi-stage builds, running as a non-root user, removing package managers and shells where possible, setting a read-only root filesystem, pinning base images by digest and rebuilding regularly to pick up patches.

Example

A Dockerfile uses a distroless base, copies only the compiled binary and sets USER 10001.

Exam tip

Running as root and bloated base images are the classic container findings.

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