Following a Failure of Services in the Network, an Administrator

Following a failure of services in the network, an administrator discovered that the configuration in one of the enterprise routers had been changed. What actions can be taken by the administrator to prevent further changes? (Choose three)

A) The administrator should limit access by setting the login privilege of users to 0.
B) The administrator should configure AAA to manage user authorization on the router.
C) The administrator should configure an ACL to allow only the administrator to manage the router.
D) The administrator should configure port-security on the router.