IDaaS provides a shared cloud layer for authentication and access governance across multiple applications, while separate system by system management leaves each platform to enforce its own rules. The first approach improves consistency, scalability, and administration efficiency. The second can work for small environments, but it usually becomes harder to maintain as the number of users, apps, and access requirements grows.
Why IDaaS Changes the Operating Model
IDaaS changes identity from a collection of separate controls into a shared layer that handles sign-in, policy enforcement, and access decisions across multiple systems. That matters because the control point moves from each application team to a central service, which usually improves consistency, reduces duplicated admin work, and makes it easier to enforce common rules such as MFA, lifecycle events, and access reviews.
In a separate-by-system model, every platform owns its own users, roles, and policies. That can be acceptable when the environment is small or highly isolated, but it creates fragmentation: different apps drift into different rules, different revocation timing, and different audit quality. The practical difference is not just convenience, it is whether identity governance is normalized or repeatedly re-implemented.
For practitioners, the real comparison is central policy enforcement versus local autonomy. IDaaS is usually strongest when many applications need the same identity standards, while per-system management may still fit edge cases where the systems cannot integrate cleanly or have different trust boundaries.
Where Separate System Management Breaks Down
Managing identity access separately in each system tends to increase the number of places where the same decisions must be repeated. That makes joiner-mover-leaver processing slower, raises the chance of stale access surviving after a role change, and increases the odds that one application has stricter controls than another. The result is often inconsistent entitlement quality, not just extra administration.
The model also weakens visibility. When access is spread across platforms, teams must reconcile multiple logs, review cycles, and approval paths before they can answer basic questions such as who has access, why they have it, and whether it still matches current duties. If an organisation relies on manual processes, that burden usually grows faster than headcount does.
Separate management can still be a rational choice where systems are few, business rules are highly unique, or integration is limited. The trade-off is that the organisation accepts more local control in exchange for more operational variance and more effort to keep governance aligned.
What IDaaS Does Better and What It Still Depends On
IDaaS is strongest when the goal is standardisation: one authentication layer, one policy model, and one place to coordinate provisioning, deprovisioning, and access governance. That usually makes it easier to scale across SaaS applications, reduce duplicated password handling, and apply consistent access review discipline. It can also simplify user experience through SSO, which lowers friction without removing the need for strong policy.
That said, IDaaS is not a substitute for good application authorization design. The shared layer can authenticate the user and pass identity context, but each application still has to decide what that user may do inside the app. A strong deployment therefore separates central identity control from local application authorization rather than assuming the identity platform can solve both.
For implementation decisions, the important question is whether the target systems can reliably consume the shared identity layer and whether the organisation can operationally own the central control plane. If either is weak, the platform may become another layer to manage instead of a simplifier.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5 sets the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-2 — Identification and Authentication (Organizational Users) | Shared identity layers centralize authentication across many applications. |
| AC-2 — Account Management | IDaaS and per-system models differ most in provisioning and deprovisioning discipline. | |
| AC-6 — Least Privilege | The comparison hinges on consistent entitlement scoping across systems. | |
| Recommendation — Use IA-2 to standardize user authentication through the central identity service. Apply AC-2 to centralize account lifecycle events and remove stale access promptly. Enforce AC-6 so each application grants only the access each role needs. | ||
| ISO/IEC 27001:2022 | A.5.15 — Access control | The topic is fundamentally about how access is governed across systems. |
| A.5.16 — Identity management | IDaaS is a centralised identity management model versus local per-system control. | |
| A.5.18 — Access rights | The main trade-off is how access rights are granted, reviewed, and revoked. | |
| Recommendation — Implement A.5.15 to keep access rules consistent across the identity estate. Use A.5.16 to manage identities centrally and reduce duplicated administration. Apply A.5.18 to review and revoke access rights consistently across applications. | ||
Practitioner Guidance
What to prioritise: Start with the applications that create the most access churn, audit friction, or offboarding risk. Those are usually the clearest candidates for a shared identity layer because the administrative payoff is immediate.
What to verify: Confirm that the chosen approach gives you a single view of provisioning, deprovisioning, and access review evidence. If you cannot answer who has access and why within one review cycle, the operating model is still too fragmented.
Decision rule: Use IDaaS when you need repeatable governance across multiple systems and can tolerate a central dependency. Keep system-by-system control only when the applications are too isolated, too bespoke, or too constrained to participate in a shared model.
Practitioner takeaway: The key difference is not cloud versus local administration, it is whether identity becomes a shared governance service or remains a repeated task inside each application team.
Related resources from NHI Mgmt Group
- What is the difference between managing password access through a central identity provider and managing it separately in each application?
- What is the difference between reviewing human access and reviewing NHIs?
- What is the difference between role-based access and API key governance for NHI security?
- What is the difference between patching a vulnerability and reducing identity blast radius?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 30, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
