What is a service principal?¶

A service principal is a technical identity used by an application, service or automation to access resources.

It is common in cloud and enterprise identity systems.

Avoid this assumption: That activity recorded against a service principal represents a human user logging in through that account. Usually, it represents software acting under granted permissions.

A service principal may authenticate using a certificate, secret, managed identity or another non-interactive method. It may access APIs, storage, databases, cloud resources or administrative functions.

Logs may contain the service principal’s name, application ID, object ID, permissions, source address, token details and action. These records can establish what the application identity did and which resources it accessed.

But the service principal does not itself identify the person behind the activity. One or more administrators may have created it, granted permissions or controlled its credentials. The application may then operate automatically for months.

Investigators should identify the associated application, owner, credentials, permissions and intended purpose. Ask whether the identity is single-tenant or multi-tenant and which systems use it.

Preserve creation and consent records, role assignments, credential changes, sign-in events and linked API or audit logs. Check whether secrets or certificates were exposed, renewed or used from unexpected locations.

Where misuse is suspected, distinguish between compromise of the service principal, abuse by an authorised administrator and normal automated activity.

Operational takeaway¶

A service principal is a non-human application identity, so its logs show software acting under assigned permissions and require separate evidence to identify who created, controlled or misused it.