The 'Okta User Session Impersonation' detection rule identifies instances where a user initiates session impersonation, gaining access with the privileges of the impersonated user. Such behavior typically indicates unauthorized administrative activity and should only happen under expected and approved circumstances. The rule triggers when an event with the action 'user.session.impersonation.initiate' is detected within the Okta system. Investigation steps involve confirming the actor's identity, reviewing timing, and analyzing all activities linked to the impersonated account. In case of unauthorized impersonation, the response involves suspending the impersonator's account and reviewing security policies to prevent future incidents.