What is immutable backup?
Short answer: An immutable backup is a recovery point that cannot be modified or deleted for a defined retention window, including by an administrator account.
Definition
Immutability answers an operational question: whether anyone (including an attacker with privileged credentials) can alter or delete copies before they are needed. An immutable backup keeps the recovery point as it was written, for as long as the retention policy requires. It is not encryption, it is not an air gap by itself, and it is not a guarantee that the service will be restored.
Why it matters
In an incident, production and copies are often the same target. If copies can be encrypted, changed or emptied, backup stops being a recovery path.
Immutability narrows that path of destruction. It lets copies be treated as evidence of a point in time, not as another file that an administrator (or an attacker who already is one) can rewrite.
What it protects, and what it does not solve alone
Conceptually, immutability protects the integrity of the recovery point against change and deletion during retention. It does not set RPO, it does not shorten RTO, and it does not run the restore.
It also does not replace isolation, off-site copies, or a rehearsed procedure. An immutable point that nobody knows how to restore, or that sits in the same compromised domain with no further control, does not close the problem.
Relationship with recovery and cyber recovery
Recovery is returning a service to a usable state. Immutability is a condition of the copies, not the act of recovering. You still need to know what to restore, in what order, and to have practised it.
Cyber recovery assumes an attacker has reached production and may also try to destroy the copies. Immutability is then a requirement of that path, not a synonym for cyber recovery.
In the Azuba model
Data Protection & Resilience treats immutability as a capability of the copies: a condition so the recovery point still exists when it is needed.
In Data Protection & Resilience, Rubrik covers immutable copies together with cyber recovery. Keepit covers immutable copies of SaaS outside the provider. ExaGrid, in Data & AI Infrastructure, provides immutability at the backup target.
Continue
Does immutable backup guarantee there will be no ransomware?
No. It reduces the ability to destroy the recovery path. It does not prevent access to production, and it does not restore the service by itself.
Is immutable the same as air-gapped?
No. Immutability prevents the recovery point from being altered. Isolation (including an air gap) limits who can reach those copies. They can be combined; they are not synonyms.