The first line of defense against illicit use of, or threats to, computer resources and sensitive information is a strong authentication and process.

Authorization process

Explanation

Authorization is a security measure to determine the access levels or user/client rights to use to system resources like files, computer programs, data and other features on a computer. Authorization process is the process of granting or denying access to a network resource that allows the user access to various resources based on the his/her identity.

Most web security systems are based on a two-step Authorization process. The first step ensures and approves the user's identity, that is authentication and the second stage is authorization, which allows the user to access the various resources based on the user's identity.

Therefore the first thing you should do when you suspect "illicit use of, or threats to, computer resources and sensitive information is a strong authentication and authorization process".