AC.L2-3.1.3  

Reference: CMMC v2.13

Family: AC

Level Introduced: 2

Title: Control CUI Flow

Practice:
Control the flow of CUI in accordance with approved authorizations.

Further Discussion:
Typically, companies will have a firewall between the internal network and the internet. Often multiple firewalls or routing switches are used inside a network to create zones to separate sensitive data, business units, or user groups. Proxy servers can be used to break the connection between multiple networks. All traffic entering or leaving a network is intercepted by the proxy, preventing direct access between networks. Companies should also ensure by policy and enforcement mechanisms that all CUI allowed to flow across the internet is encrypted.

Example 1
You configure a proxy device on your company’s network. CUI is stored within this environment. Your goal is to better mask and protect the devices inside the network while enforcing information flow policies. After the device is configured, information does not flow directly from the internal network to the internet. The proxy device intercepts the traffic and analyzes it to determine if the traffic conforms to organization information flow control policies. If it does, the device allows the information to pass to its destination [b]. The proxy blocks traffic that does not meet policy requirements [e].

Example 2
As a subcontractor on a DoD contract, your organization sometimes needs to transmit CUI to the prime contractor. You create a policy document that specifies who is allowed to transmit CUI and that such transmission requires manager approval [a,c,d]. The policy instructs users to encrypt any CUI transmitted via email or to use a designated secure file sharing utility [b,d]. The policy states that users who do not follow appropriate procedures may be subject to disciplinary action [e].

Potential Assessment Considerations
• Are designated sources of regulated data identified within the system (e.g., internal network and IP address) and between interconnected systems (e.g., external networks, IP addresses, ports, and protocols) [c]?
• Are designated destinations of regulated data identified within the system (e.g., internal network and IP address) and between interconnected systems (external networks and IP addresses) [c]?
• Are authorizations defined for each source and destination within the system and between interconnected systems (e.g., allow or deny rules for each combination of source and destination) [d]?
• Are approved authorizations for controlling the flow of regulated data enforced within the system and between interconnected systems (e.g., traffic between authorized sources and destinations is allowed and traffic between unauthorized sources and destinations is denied) [e]?

Source: CMMC v2.13