Backup (3-2-1)

A backup is a recoverable copy of your data, and the 3-2-1 rule is the durable standard: keep three copies, on two different media, with one off-site (or offline/immutable). The off-site, offline copy is what survives a ransomware attack that encrypts everything it can reach over the network. A backup you have never restored from is a hope, not a plan — test restores regularly.