How can organisations reduce identity risk without replacing every legacy system?

Why This Matters for Security Teams

Replacing every legacy platform is rarely realistic, but leaving old identity paths untouched is what keeps risk hidden. The practical problem is not system age alone; it is the concentration of privileged accounts, shared secrets, stale service credentials, and unclear ownership inside systems that still run the business. NHI Management Group research shows why cleanup must be prioritized, not abstracted: only 5.7% of organisations have full visibility into service accounts, and 97% of NHIs carry excessive privileges in many environments.

That means the fastest reduction in identity risk usually comes from finding the identities with the highest blast radius and fixing them first. The NIST Cybersecurity Framework 2.0 supports that risk-based approach, while NHIMG’s Ultimate Guide to NHIs shows how common it is for secrets and service accounts to remain unmanaged long after teams believe they have already addressed them.

Security teams often over-focus on standardisation projects and under-focus on the identities that can already be abused today. In practice, many organisations discover the most dangerous legacy account only after a routine application change or incident review exposes it.

How It Works in Practice

The most effective pattern is to build a remediation queue around identity risk, not around application migration. Start by inventorying accounts, API keys, certificates, service principals, and embedded secrets across legacy systems. Then rank them by privilege, data sensitivity, external exposure, and whether the identity can be rotated or revoked without breaking core operations.

That list becomes a business-owned cleanup plan. Each system owner receives a short set of actions: remove orphaned access, replace shared credentials with named workload identities where possible, shorten secret lifetimes, and add monitoring for any identity that must remain in place. This is often more achievable than a full platform replacement because it isolates change to the identity layer first.

Practitioners should pair that cleanup with controls that reduce standing risk immediately:

• Rotate the highest-risk secrets first, especially those used by privileged automation.
• Replace hard-coded credentials in code, scripts, and CI/CD jobs with managed secret retrieval.
• Apply least privilege to legacy service accounts even if the application itself cannot be modernised.
• Use compensating controls such as network restriction, token TTL limits, and alerting on unusual use.

NHIMG’s Top 10 NHI Issues is useful here because it frames the recurring failure modes that create residual risk. For implementation depth, teams should also consult the OWASP OWASP NHI Top 10 for identity attack paths that still apply even in older architectures.

These controls tend to break down when legacy applications require shared credentials across tightly coupled batch jobs, because revocation and rotation can interrupt business-critical processing.

Common Variations and Edge Cases

Tighter identity control often increases operational overhead, so organisations need to balance risk reduction against application stability and support capacity. That tradeoff is real in mainframes, vendor-managed platforms, and deeply embedded OT-adjacent systems where identity change is slow or partially outsourced.

Current guidance suggests using compensating controls when direct remediation is not feasible. For example, if a legacy system cannot support modern federation, keep the account but narrow its reach with network segmentation, IP allowlisting, stronger logging, and time-bound access approvals. If a workload depends on a static credential, reduce exposure by storing it in a managed vault, setting an explicit rotation schedule, and assigning a business owner who can approve exceptions.

There is no universal standard for this yet, but the working principle is consistent: reduce standing privilege wherever possible, then document and monitor the exceptions that remain. The objective is not to prove every legacy system is modern. It is to ensure the identities attached to those systems are visible, owned, and constrained enough to lower breach impact.

In practice, teams make the biggest progress when they treat legacy identity cleanup as an ongoing control program rather than a one-time modernisation project, and the highest-risk exceptions are often the first place attackers look.

Related resources from NHI Mgmt Group

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• How should security teams reduce identity risk in compliance automation programmes?