What breaks when machine accounts are not marked as not delegable?

What breaks is the assumption that only users need delegation protection. If sensitive machine accounts remain delegable, downstream services can request tickets or act on behalf of identities that should never be represented, which can open a route to certificate abuse, DCSync-style access, and domain compromise.

Why This Matters for Security Teams

The risk is not just misconfiguration, it is representational power. When a machine account is allowed to delegate, downstream systems can obtain service tickets or act in that account’s context even when the account was never meant to be impersonated. That changes a routine service identity into a path for privilege extension, ticket abuse, and domain-wide escalation. NHI Mgmt Group notes that 97% of NHIs carry excessive privileges, which makes delegation mistakes especially dangerous in real environments.

This issue sits at the intersection of identity governance and Kerberos trust boundaries. It is easy to focus on password strength or vaulting and miss the delegation bit entirely. Yet once a machine account can be represented by another principal, attack paths become easier to chain, especially in environments with broad service-to-service trust. The NIST Cybersecurity Framework 2.0 reinforces that identity governance must protect both access and trust relationships, not just authentication secrets. In practice, many security teams encounter delegation abuse only after lateral movement has already reached sensitive infrastructure, rather than through intentional review of machine account delegation settings.

How It Works in Practice

Marking a machine account as not delegable tells the directory and authentication stack that the identity must not be forwarded, impersonated, or used as a source for downstream delegation. In Kerberos environments, that reduces the chance that a compromised service can request tickets on behalf of an identity that was never supposed to be represented. This is especially important for service accounts tied to certificate authority systems, domain controllers, backup agents, and management tooling.

Operationally, the control should be paired with other identity safeguards:

• Review machine accounts that have unconstrained or overly broad delegation settings.
• Separate high-value service identities from general-purpose application accounts.
• Use least privilege and explicit trust boundaries for service-to-service access.
• Monitor for anomalous service ticket requests, impersonation patterns, and unusual authentication flows.
• Align delegation settings with incident response so high-risk accounts can be rapidly isolated.

This is not only about user impersonation. A delegable machine account can become the bridge that lets an attacker move from a single compromised workload into credential theft, service abuse, or directory replication attempts. NHI Mgmt Group’s Schneider Electric credentials breach coverage underscores how identity compromise can cascade once trust is extended too far. For policy mapping, NIST Cybersecurity Framework 2.0 is most relevant where it drives access control review, monitoring, and continuous authorization decisions. These controls tend to break down when legacy Windows domains mix service accounts, admin tools, and broad delegation because the trust model becomes too opaque to validate consistently.

Common Variations and Edge Cases

Tighter delegation controls often increase operational overhead, requiring organisations to balance service continuity against reduced impersonation risk. That tradeoff is real in environments with older applications, third-party integration points, or application pools that depend on Kerberos delegation for normal function. Current guidance suggests treating those exceptions as temporary and documented, not as a reason to leave machine accounts broadly delegable.

Some teams also confuse not delegable with fully secure. It is only one control, and it does not replace strong secret handling, rotation, tiering, or segmentation. In mixed Windows and cloud environments, delegation settings may be enforced differently across platforms, so identity teams need to validate the actual runtime path rather than assume policy translates cleanly everywhere. NHI Mgmt Group research shows that 80% of identity breaches involved compromised non-human identities, which is why this setting should be reviewed alongside broader NHI exposure. Best practice is evolving, but there is no universal standard for when every machine account must be non delegable; high-value and privileged identities should be the first priority.

Related resources from NHI Mgmt Group

• What breaks when service accounts and tokens are treated as low-risk identities?
• Why do non-human identities create more risk than many human accounts?
• Why do non-human identities create more remediation risk than many human accounts?
• What are common vulnerabilities associated with service accounts in AI deployments?