NIST 800-171 - Split-Tunneling (3.13.7)
Prevent remote devices from simultaneously establishing non-remote connections with the information system and communicating via some other connection to resources in external networks.
3.13.7[a]
Determine if: remote devices are prevented from simultaneously establishing non-remote connections with the system and communicating via some other connection to resources in external networks (i.e., split tunneling).
POTENTIAL ASSESSMENT METHODS AND OBJECTS
1
Examine: System and communications protection policy; procedures addressing boundary protection; system security plan; system design documentation; system hardware and software; system architecture; system configuration settings and associated documentation; system audit logs and records; other relevant documents or records].
2
Interview: System or network administrators; personnel with information security responsibilities; system developer; personnel with boundary protection responsibilities].
3
Test: Mechanisms implementing boundary protection capability; mechanisms supporting or restricting non-remote connections].
1) System and communications protection policy
2) procedures addressing boundary protection
3) system security plan
4) system design documentation
5) system hardware and software
6) system architecture
7) system configuration settings and associated documentation
8) system audit logs and records
9) other relevant documents or records
This requirement is implemented in remote devices (e.g., notebook computers, tablets) through configuration settings to disable split tunneling in those devices, and by preventing configuration settings from being readily configurable by users. This requirement is implemented in the system by the detection of split tunneling (or of configuration settings that allow split tunneling) in the remote device, and by prohibiting the connection if the remote device is using split tunneling. Split tunneling might be desirable by remote users to communicate with local system resources such as printers or file servers. However, split tunneling would allow unauthorized external connections, making the system more vulnerable to attack and to exfiltration of organizational information.