A tar archive is a file format that bundles multiple files and their metadata into one container. It does not compress by itself; its main job is to preserve file names, paths, timestamps, and permissions so data can be moved or restored as a unit.
In cyber security, tar archives matter because extraction is a filesystem operation, not just parsing bytes. If software trusts an attacker-controlled archive, crafted paths or file types can cause files to be written outside the intended directory, overwrite data, or expose sensitive content. This makes tar handling a common attack surface in installers, CI jobs, backup tools, and upload processors. Defenses include validating paths, rejecting unexpected entries, extracting with least privilege, and using isolated temporary directories before moving only approved files into place.