SI.L2-3.14.7

Define authorized use of your systems. Create an acceptable use policy to establish the baseline for how users access devices, internal network services, and the internet. Define authorized use by specific roles such as: user, administrator, and technician. After authorized use is defined, identify unauthorized use of systems.

Monitor systems by observing audit activities from the system logs. This can be accomplished in real time using automated solutions or by manual means. To identify unauthorized use, leverage existing tools and techniques, such as:

• intrusion detection systems;
• intrusion prevention systems;
• malicious code protection software;
• scanning tools;
• audit record monitoring software; and
• network monitoring software.

This requirement, SI.L2-3.14.7, which deals with identifying unauthorized use of organizational systems, is related to requirements: AC.L2-3.1.1, AU.L2-3.3.1, IA.L2-3.5.1, and IA.L2-3.5.2. All of these requirements help create the building blocks that support SI.L2-3.14.7.

Example 1

You are in charge of IT operations. You need to ensure that everyone using an organizational system is authorized to do so and conforms to the written authorized use policy. To do this, you deploy an application that monitors user activity and records the information for later analysis. You review the data from this application for signs of activity that does not conform to the acceptable use policy [a,b].

Example 2

You are alerted through your Intrusion Detection System (IDS) that one of your users is connecting to a server that is from a high-risk domain (based on your commercial domain reputation service). You investigate and determine that it’s not the user, but instead an unauthorized connection attempt [b]. You add the domain to your list of blocked domains to prevent connections in the future.

Potential Assessment Considerations

• Is authorized use of systems defined (e.g., data types permitted for storage or processing, personnel authorized to access, times or days of permitted use, permitted software) [a]?
• Is unauthorized use of systems defined (e.g., not authorized to use systems for bitcoin mining, not authorized for pornographic content, not authorized to access gambling games/content) [b]?