A backup copy is a stored duplicate of data kept so systems can be restored after loss, corruption, deletion, or ransomware. Backups may be full, incremental, or snapshot-based, and they are usually protected by separate access controls and retention policies. In security, backups are essential for continuity, but they also expand the data footprint: old email, files, and logs may remain available long after the original system changes.
That matters because a backup can preserve sensitive content that users assume is gone. Attackers often try to delete or encrypt backups to block recovery, while defenders use offline or immutable backups to resist that tactic. In corporate email environments, backup copies can also create privacy and governance issues, because archived messages may still contain personal data and administrative access must be tightly controlled.