Kerberos Least Privilege: Trust Without Surrender

Least privilege turns Kerberos from a wide-open gate into a locked corridor. It limits what each principal, ticket, or service account can do. The system still runs smoothly, but exposure is cut to the bone. That matters when one stolen credential can pivot across domains in seconds.

In Kerberos, least privilege starts with the Key Distribution Center. Constrain service accounts so their tickets grant only the permissions needed for their specific function. Assign short ticket lifetimes. Reduce the scope of delegation, and never issue unconstrained delegation unless absolutely required.

Audit service principal names. Remove stale accounts. Rotate keys often. Verify that role-based access control matches the actual operational need. The tighter each account’s clearance, the smaller the blast radius when—not if—something fails.

Avoid granting admin tickets to automated processes. Break large services into smaller ones with separate accounts. Monitor ticket requests, renewals, and failures for patterns of abuse. Combine network segmentation with Kerberos constraints so that even a valid ticket cannot breach restricted segments.

Secure by default. Grant only what the task demands. Deny everything else. Kerberos least privilege is not a one-time setup — it is an active posture, adjusted with every code change, service deployment, and hardware shift.

Build your Kerberos deployment on the principle that no single compromise should ever become a full compromise. Cut the surface area. Limit the power of every account. Keep secrets short-lived. Let the trust model serve its true purpose — authentication without surrender.

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