Is an untested backup really a backup

A copy is useful when you know what it contains, how old it is and how to put it back into service. Instant synchronization can faithfully replicate deletion or malicious encryption, so synchronization alone is not a complete backup strategy.

ANSSI and CISA guidance stresses backups protected from the normal environment, including offline or otherwise isolated copies where the risk warrants it. The goal is to prevent one compromised account or ransomware incident from deleting every copy with the same permissions.

The “3-2-1” rule is a useful memory aid, not a substitute for requirements. A transactional database, family photographs and a server configuration change at different rates and have different recovery goals. Acceptable data loss and acceptable downtime should be explicit.

Terabytes of backup are little help if restoration takes days while the service must return in hours. Throughput, dependencies, encryption keys, administrator accounts and restoration order should be known before the incident.

Regularly restore individual files, then run broader exercises for critical services. Record results, durations and missing dependencies. A green backup log is not sufficient proof if nobody has actually read the data back and rebuilt what matters.