Immutable Backups: The Truth

Backup is your last line of defense—but what happens when even your backups are targeted? Ransomware attacks have evolved, and many are now designed to encrypt or delete backup files, leaving you with nothing to restore.

That’s where immutable backups come in. In this article, I’ll explain what immutable backups are, why they’re critical for modern IT environments, and how to implement them using real-world tools and strategies.

What Are Immutable Backups?

An immutable backup is a backup copy that cannot be altered, deleted, or encrypted within a set period of time—no matter what. Even if an attacker gains access to your environment, they can’t touch these protected files.

Immutability is usually enforced at the storage level (e.g., object lock on S3, hardened Linux repos) or via software features in backup tools like Veeam or Commvault.

Why Immutability Matters in 2025

Attackers know that backups are the key to recovery, which is why they target them first. Immutability stops them in their tracks.

Here’s why it matters:

  • Prevents tampering from ransomware or rogue insiders
  • Ensures data integrity during audits or legal holds
  • Gives peace of mind for mission-critical data
  • Strengthens your disaster recovery posture

Without immutable backups, your recovery plan is at risk.

How to Implement Immutable Backups

There’s no one-size-fits-all, but here are the most common methods:

1. Object Storage with Object Lock (S3 or compatible)

Platforms like AWS S3 or Wasabi support object lock, which allows you to set WORM (Write Once Read Many) policies.

Use case: Backup repositories that need to be ransomware resilient.

2. Hardened Linux Repositories (Veeam-specific)

Veeam Backup & Replication allows backups to be written to a Linux server configured with immutability settings, using XFS with extended attributes.

Use case: On-prem backup with no reliance on cloud.

3. Immutable Snapshots in NAS/Storage Arrays

Storage vendors like NetApp or Dell offer snapshots that are locked from deletion or modification for a specified time.

Use case: Local fast restore points with immutability.

4. Air-Gapped and Offline Backups

While not technically immutable, backups stored offline or disconnected from the network provide strong protection.

Use case: Ultimate fallback for critical data.

Best Practices for Using Immutable Backups

  • Combine immutability with access control (MFA, role separation)
  • Set reasonable retention periods—enough for rollback, not too long for storage costs
  • Monitor and test restores from immutable copies regularly
  • Don’t rely solely on immutability—layered security still matters

Immutable backups aren’t just a nice-to-have—they’re a necessity in today’s threat landscape. Whether you’re protecting Active Directory, databases, or full VMs, adding immutability gives your organization a powerful recovery edge.

If your backup strategy doesn’t include immutability yet, now’s the time to change that. Because when the worst happens, you’ll be glad you did.