Air-gapped Nextcloud: what disconnecting your server really protects, and what it does not
Nextcloud argues that an air gap is the best defence against AI-driven attacks. The idea is sound, but it is a vendor pitch with real limits. Here is what it means for anyone running their own cloud.
By Andrew Ingleton · Published
On 27 October, Nextcloud published a blog post arguing that physically isolating systems is one of the few reliable ways to stop automated, AI-assisted attacks. It is vendor marketing, and the company is promoting a webinar on air-gapped installations, so it deserves a careful read. The underlying idea is old and worth understanding, particularly if you already keep a Nextcloud server updated at home or in a small organisation.
What Nextcloud is arguing
The post says attacks are becoming faster, larger in scale and less dependent on human operators. It cites reported incidents in which AI models, during security evaluations, got around isolation controls or accessed third-party systems, and it describes criminal operations that use several AI agents to scout, exploit and exfiltrate data. Those incident reports come from the AI companies' own disclosures, as the article itself notes, and we have not verified them.
From there the logic is simple: software restrictions can be bypassed, but an agent still needs a network path to reach its target. A system with no external connection offers none. Nextcloud claims its platform can run fully offline with no dependence on outside cloud services, with updates prepared elsewhere and moved across through a controlled process.
What an air gap does and does not do
Nextcloud concedes the key limits itself. An air gap addresses remote, network-based attacks. It does not stop:
- Physical access to the machine or the building.
- Removable media carrying malware across the gap, the classic route for isolated systems.
- Compromised devices that are later connected to the isolated network.
- Insiders and weak update procedures.
- Flaws inside the system itself once something malicious is on it.
The trade-off for a home or small-office server
Most readers will not run a truly air-gapped system, and for good reason: the price of isolation is convenience. There is no remote access, no mobile sync from outside the house, no push notifications and no automatic security updates. Unpatched software is its own risk, and if you skip the manual update routine you can end up less safe than a well-maintained, internet-facing server behind a VPN.
A more realistic middle path, which is our own suggestion rather than Nextcloud's, is to reduce exposure rather than remove it:
- Keep the server off the public internet and reach it only through a VPN.
- Put it on its own network segment so other devices cannot freely talk to it.
- Keep an offline, tested backup so that ransomware cannot reach every copy.
- Apply updates promptly, since most real-world compromises exploit known flaws.
A genuine air gap makes sense for sensitive archives, such as a small set of documents you rarely need to change. For everything else, think of it as one end of a scale and decide where on that scale your data deserves to sit.
