An air gapped backup is a copy of data with no automated connection to the systems it protects, so ransomware or an attacker using stolen admin credentials can’t reach it from the production network. The NIST glossary, quoting CNSSI 4009-2022, sets the strict test: no physical connection, and any logical connection made manually, “under human control.” As of October 2026, most vault products reviewed below use logical isolation instead (separate accounts, credentials and locked retention); NIST SP 800-209 recognizes less strict forms of air-gapping and says to weigh each against the value of the data and the capabilities of the adversary.
Related backup and resilience coverage is listed in Enterprise Techie’s topic index.
In this guide
Key facts
| Term | What the source says | Source |
|---|---|---|
| Air gap | No physical connection; any logical connection is manual | NIST glossary (CNSSI 4009-2022) |
| Strict vs less strict air gap | Full physical and network separation, or data ports opened only for limited sync windows | NIST SP 800-209 (October 2020) |
| Offline backup | Kept offline because many ransomware variants seek out accessible backups | CISA #StopRansomware Guide (2023) |
| Immutability | Data locked after creation against alteration or deletion | NIST SP 800-209 |
| Cyber-attack recovery copy | Hardened, locked, isolated; restored to an isolated staging environment | NIST SP 800-209, section 4.7 |
What counts as an air gap
The glossary definition is demanding. A backup target fed by a scheduled, automated network job doesn’t meet it, even if a firewall closes the path between jobs. NIST SP 800-209 is looser: recommendation IS-SS-R8 says strict implementations “should provide full physical and network-level separation,” and acknowledges less strict technologies, also called air-gapping, that open data ports only for periodic syncs with production.
Ransomware guidance mostly says “offline.” CISA’s #StopRansomware Guide calls for offline, encrypted backups of critical data because “many ransomware variants attempt to find and subsequently delete or encrypt accessible backups.” The UK NCSC’s ransomware guidance asks for offline backups kept separate from networks and systems, ideally offsite, or in a cloud service designed for the purpose.
Physical air gap: offline media
The NCSC’s on-premises backup principles describe the classic form: backups on durable media such as magnetic tape, stored off the network somewhere safe, with floods and fires in mind when choosing the location. Malware can’t encrypt a cartridge on a shelf, and a stolen domain admin password can’t delete it remotely.
The exposures are physical: media is connected while being written, and anyone with access can remove it. The NCSC asks for regular reviews of who can physically reach the backup system and media; NIST (IS-SS-R4) wants recovery copies stored off-site. The cost is labor for rotation, transport and custody. Restores wait on retrieval and loading, which normally makes this the slowest path back.
Logical air gap: isolation without unplugging
A logical, or virtual, air gap isolates through configuration. The NCSC’s post Offline backups in an online world (2019) notes that cloud storage can’t be unplugged, so identity controls, backup clients that hold no valid credentials while idle, and access rules that refuse connections while storage is “cold” stand in for the cable.
NIST SP 800-209 lists what the separation should cover: separate storage (separate accounts in public clouds), management systems that regular production or backup credentials can’t reach, and access limited to a narrow group with dedicated credentials. Because configurations drift, NIST recommends isolation reviews at least yearly, and possibly quarterly and after every major change for sensitive systems. Restores run at network speed; the cost is a second identity and management plane plus audits.
Air gapped vs immutable backup
NIST SP 800-209 defines immutability as “the ability to lock data after it has been created, thereby preventing it from alteration or deletion,” and lists immutable storage after the air gap recommendation as something that “could help further isolate and protect recovery data.”
Amazon S3 Object Lock uses a write-once-read-many (WORM) model with two modes. In governance mode, users with the s3:BypassGovernanceRetention permission can override retention. In compliance mode, no user, including the root user, can overwrite or delete a locked version or shorten its retention; AWS notes the only early way out is deleting the AWS account. Microsoft’s Azure Backup immutable vault splits similarly: “enabled” is reversible, while “enabled and locked” is irreversible and moves backups to WORM storage where Azure supports it.
WORM is regulatory vocabulary too: SEC Rule 17a-4(f) lets broker-dealers keep records “exclusively in a non-rewriteable, non-erasable format” or with a time-stamped audit trail. CISA cautions that immutable storage “does not meet compliance criteria for certain regulations” and that misconfiguration can impose significant cost.
The difference: immutability limits what anyone can do to data they can reach; an air gap limits who can reach it. A lock doesn’t stop someone with read access from copying data out, and the NCSC warns that attackers can delete or modify encryption keys instead of backups. An air gap without immutability is exposed whenever it connects.
Recovery vaults and isolated recovery environments
NIST SP 800-209 separates ordinary recovery copies from cyber-attack recovery copies that are “hardened, locked, and kept in isolation,” recommended for critical and sensitive systems. Vendors sell this as a cyber recovery vault. NIST (IS-SS-R7) wants those copies restored onto “an isolated staging (or air-gapped) environment” rather than directly onto target systems. That staging area is the clean room inside an isolated recovery environment (IRE); Cohesity’s Clean Room Solution and Commvault’s Cleanroom Recovery are vendor examples.
CISA asks for restoration on a clean network, admitting only clean systems to any recovery VLAN. The NCSC says to scan backups for malware first, since ransomware may have replicated into them before discovery. Enterprise Techie’s cyber recovery vault comparison treats the IRE as the umbrella over vault storage and clean-room compute. This is the costliest approach, and validation adds time before production cutover.
Threat by threat
Ransomware that targets backups. The NCSC’s ransomware-resistant backups guidance says actors often target backups early in a destructive attack. Offline media removes the network path, a separated logical gap removes the credential path, and a compliance-mode lock removes the ability to change data during retention.
Stolen admin credentials. The NCSC wants backup admin accounts separate from the rest of the network. Governance-mode locks fail if the stolen identity holds the bypass permission. AWS Backup’s logically air-gapped vault keeps backups in a service-owned account and can use multi-party approval to restore them if the owning account is lost. Azure’s multi-user authorization requires permission on a Resource Guard owned by a different user, optionally in another tenant.
Insider deletion. The NCSC’s cloud backup principles suggest forbidding destructive requests from customer accounts, administrators included, with exceptions authorized out-of-band, and delaying deletions behind alerts. For tape, the control is custody reviews.
What none of them fix. The NCSC says its backup principles don’t address data theft for extortion. Offline and immutable copies also preserve dormant malware, so restores need scanning; the storage-native ransomware detection analysis covers one way to find a clean restore point.
What vendors call it
Vendors’ own descriptions as of October 2026, alphabetical, not ranked.
| Vendor | Offering | Vendor’s description |
|---|---|---|
| AWS | AWS Backup logically air-gapped vault | Compliance-mode Vault Lock; backups held in a service-owned account |
| Cohesity | FortKnox | Immutability, encryption and a “virtual air gap”; managed vault on AWS, Azure and GCP |
| Commvault | Commvault AirGap | “Air-gapped, immutable cloud storage” |
| Dell | PowerProtect Cyber Recovery | “Operational air gap”: a vault with its own controls, credentials and management plane; physical or logical separation |
| Google Cloud | Backup and DR backup vault | “Isolated, immutable, and indelible storage” with project-level identity isolation |
| Microsoft | Azure Backup immutable vault | Data stored “in isolation from production workloads”; locked immutability is irreversible |
| Veeam | Veeam Data Cloud Vault | “Always immutable and logically air-gapped from production,” on Azure Blob storage |
By the glossary’s test, the cloud services here are logical rather than strict air gaps. Before buying any air gap backup product, ask whose account holds the data, which credentials can delete it or shorten retention, and whether a full identity-provider compromise reaches it. For on-premises targets, see the immutable backup storage comparison.
Comparison table
| Approach | Protects against | Restore speed | Cost to run | Sources |
|---|---|---|---|---|
| Physical air gap (offline tape or media) | Network ransomware; remote deletion | Slowest | Media handling, transport, custody | NIST glossary; SP 800-209; NCSC; CISA |
| Logical air gap | Production compromise, if identities are truly separate | Network speed | Second identity plane; isolation audits | SP 800-209; NCSC blog |
| Immutable storage (Object Lock, locked vaults) | Encryption, overwrite and deletion during retention | Fast | Low effort; locked data billed until expiry | SP 800-209; AWS; Azure; CISA |
| Managed logically air-gapped vault | Production account or tenant compromise | Network speed, often cross-account | Service fees; transfer fees vary | AWS, Microsoft, Google, vendor pages |
| Cyber recovery vault plus IRE | Reintroducing malware into production | Slower: scan and validate first | Highest: storage, compute, identities, rehearsals | SP 800-209 section 4.7; CISA; NCSC |
How to decide
- The offsite copy can be deleted from the production console: add compliance-mode immutability and separate backup admin accounts first.
- Full identity compromise is the worry: keep a copy in a separate account or tenant, with multi-user or out-of-band approval for destructive actions.
- A rogue administrator is the worry: compliance-mode locks, out-of-band approval, delayed deletion with alerts, and media custody reviews.
- Records retention rules apply: check the WORM implementation against the specific rule and the vendor’s compliance assessment.
- Tier-0 must return fast after an attack: an online immutable or vault copy plus rehearsed restores into an IRE; see the backup restore testing guide.
- The data is existential or the adversary highly capable: a strict air gap as NIST describes, accepting slow restores.
The approaches stack. The “+1” in the 3-2-1-1-0 backup rule can be immutable or air-gapped, and the ransomware recovery plan shows where the copy fits in an incident. AWS warns that locked backups can’t be deleted until their lifecycle completes, so price retention first with the backup storage cost per TB analysis.
Frequently asked questions
Is immutable backup the same as air gapped?
No. Immutability locks data against change or deletion for a retention period; an air gap removes the connection an attacker would use to reach it. NIST SP 800-209 treats immutable storage as an added layer, and the two can be combined.
What is the difference between a logical air gap and a physical air gap?
A physical air gap disconnects the media, such as tape stored offline. A logical air gap keeps storage online but isolates it with separate accounts, credentials and limited connection windows, which NIST SP 800-209 treats as less strict than full physical and network separation.
Is cloud backup air gapped?
Not by default. The NCSC notes that cloud storage can’t be unplugged, so offline-style protection depends on identity controls, clients without standing credentials and access rules that refuse connections while it isn’t in use.
What is an isolated recovery environment?
An isolated network and compute area where backups are restored, scanned and validated before reconnecting to production. NIST SP 800-209 calls it an isolated staging (or air-gapped) environment.
Does an air gapped backup protect against data extortion?
No. The NCSC notes its ransomware-resistant backup principles don’t address data theft, and advises protecting backup systems from unauthorized access like any system holding sensitive data.
Sources
- NIST CSRC Glossary: air gap
- NIST SP 800-209: Security Guidelines for Storage Infrastructure
- CISA, FBI, NSA and MS-ISAC: #StopRansomware Guide
- NCSC: Mitigating malware and ransomware attacks
- NCSC: Ransomware-resistant backups
- NCSC: Principles for ransomware-resistant on-premises backups
- NCSC: Principles for ransomware-resistant cloud backups
- NCSC blog: Offline backups in an online world
- AWS: Locking objects with S3 Object Lock
- AWS Backup: Logically air-gapped vault
- AWS Backup Vault Lock
- Microsoft Learn: Immutable vault for Azure Backup
- Microsoft Learn: Multiuser authorization using Resource Guard
- Google Cloud: Backup vaults for immutable and indelible backups
- Dell: PowerProtect Cyber Recovery
- Cohesity: FortKnox
- Commvault: Commvault AirGap
- Veeam: Veeam Data Cloud Vault
- eCFR: 17 CFR 240.17a-4 (SEC Rule 17a-4)
Last checked: October 2026. Guidance and product features change; check each source before you rely on it.
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