Container hardening is the practice of reducing risk by tightening settings, permissions, and exposed services in a container or cluster. It usually includes removing unnecessary packages, running processes as non-root, limiting Linux capabilities, enforcing read-only filesystems where possible, and disabling defaults that create extra exposure.
In cyber security, hardening matters because containers often share infrastructure, credentials, and internal network paths. A weak container can become a foothold for privilege escalation, secret theft, or lateral movement into other workloads. Defenders use hardening to shrink the attack surface before an attacker can abuse overbroad service accounts, open ports, permissive network rules, or unsafe configuration defaults. In Kubernetes, good hardening helps keep one compromised workload from turning into a cluster-wide compromise.