What happens when user groups are not used to authorise access in a Zero Trust model?

Why group-based authorisation matters in Zero Trust

In a Zero Trust model, the problem is not just whether access is allowed, but how consistently that decision can be evaluated and maintained. Group-based authorisation gives you a stable abstraction for least-privilege access, so policy can be applied once and inherited cleanly across users, devices, applications and services. That is why Zero Trust guidance consistently ties identity-centric policy to NIST SP 800-207 Zero Trust Architecture.

When groups are removed from the model, access tends to be granted one principal at a time. That can work for a small environment, but it becomes harder to explain, audit and update as the number of resources grows. It also weakens the normal separation between “who the subject is” and “what access they should have”, which makes it easier for exceptions to accumulate and for policy to drift away from the intended baseline.

Groups are also a practical way to translate business intent into enforceable access patterns. Instead of updating dozens of individual entitlements when a team changes, you update the group and let the policy follow the organisational structure. That matters in Zero Trust because the model assumes continuous enforcement, not one-off approval. Without that layer, the control plane becomes more manual and the architecture depends more heavily on perfect administration.

What breaks when authorisation is fully individualised

Individualised authorisation usually increases operational friction. Every joiner, mover and leaver event becomes more expensive because access has to be edited directly on each account or grant. At scale, that creates more room for inconsistent exceptions, especially when the same person needs access to multiple applications, environments or data sets with slightly different rules.

It also makes least privilege harder to sustain. Groups allow you to define a bounded access pattern for a role, function or context, then remove it when the condition changes. Without them, permissions often become a patchwork of one-off grants that are harder to review and easier to miss during recertification. The result is usually more overexposure, not less, even if the initial intent was to make access more precise.

This is why modern identity and access practices still favour grouped policy models such as role design, entitlement management and access review. IAM and IGA basics explains how those functions fit together, while authorisation models shows when RBAC, ABAC or ReBAC is the better fit for the policy decision.

How to preserve Zero Trust discipline without losing flexibility

The practical answer is usually not “use only groups” or “use no groups”, but “use groups as the default policy layer and add finer-grained controls where necessary”. In Zero Trust, group membership is often the right place to express baseline access, while attribute checks, device posture, context and per-request policy handle the exceptions. That keeps the model manageable without turning every decision into a bespoke entitlement.

If you need a reference architecture for doing that across people, workloads and devices, Zero Trust Identity Guide is the most direct internal starting point. Where workload or service access is the issue, Zero Trust for AI Agents is a useful example of how per-action policy and bounded privilege work when the subject is not a human user.

Risk and Threat Considerations

Removing group-based authorisation does not just add admin effort, it also increases the chance that access decisions become inconsistent across systems. That creates policy drift, weakens least privilege, and makes it easier for excess access to survive longer than intended. The risk becomes more serious in environments with many applications or frequent role changes, where manual entitlement edits are easy to miss.

Failure mechanism: access is granted and maintained as many separate individual decisions instead of one controlled policy construct, so changes are applied unevenly and exceptions accumulate.

Impact: review cycles get slower, revocation becomes less reliable, and the environment is more likely to retain permissions that no longer match business need or current trust conditions.

Practitioner Guidance

What to verify: check whether your current policy model still has a clean mapping between organisational function and effective access. If the same access pattern is being recreated repeatedly for individuals, groups are probably doing necessary governance work that is now being done manually.

Decision rule: use groups for the stable baseline, then layer exceptions only where the business case genuinely requires a narrower or temporary grant. If an exception has become common, convert it into a managed policy construct rather than leaving it as repeated manual work.

Common mistake: treating direct assignment as “more Zero Trust” because it is more granular. In practice, excessive granularity can reduce control, because it removes the reusable structure that makes review, revocation and consistency tractable.

Practitioner takeaway: Zero Trust does not mean every access decision should be bespoke. The control objective is to make access continuously enforceable and easy to change, and groups are still one of the most effective ways to keep that property intact.

Related resources from NHI Mgmt Group

• What happens when a verified user connects from a compromised device in a Zero Trust model?
• What happens when privileged accounts are given more access than they need under a zero trust model?
• What happens when access policy is not aligned with device state in a Zero Trust model?
• How should organisations use MFA within a Zero Trust model to protect remote access without creating too much user friction?