NIST Special Publication 800-171 Revision 2

Date Published: January 28th, 2021

Withdrawn on May 14, 2024. Superseded by SP 800-171 Rev. 3

Author(s): Ron Ross (NIST), Victoria Pillitteri (NIST), Kelley Dempsey (NIST), Mark Riddle (NARA), Gary Guissanie (IDA)

Note: A Class Deviation is in effect as of May 2, 2024 (DEVIATION 2024O0013). The deviation clause requires contractors, who are subject to 252.204-7012, to comply with National Institute of Standards and Technology (NIST) Special Publication (SP) 800-171 Revision 2, instead of the version of NIST SP 800-171 in effect at the time the solicitation is issued or as authorized by the contracting officer. Click Here

3.13.5: Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks.

Control Family: System and Communications Protection

Control Type: Derived

SPRS Value: 5

SPRS Supplemental Guidance: N/A

CMMC Level(s):

  • SC.L1-b.1.xi

  • SC.L2-3.13.5

Top Ten Failed Requirement:

No

Referenced in:

DFARS 252.204-7012

Derived From: NIST SP 800-53r4

  • SC-7

NIST Supplemental Guidance:

  • [SP 800-41]

  • [SP 800-125B]

Discussion:

Subnetworks that are physically or logically separated from internal networks are referred to as demilitarized zones (DMZs). DMZs are typically implemented with boundary control devices and techniques that include routers, gateways, firewalls, virtualization, or cloud-based technologies.

[SP 800-41] provides guidance on firewalls and firewall policy. [SP 800-125B] provides guidance on security for virtualization technologies.

Upon assessment, assessors must determine if- 

3.13.5[a] publicly accessible system components are identified.
3.13.5[b] subnetworks for publicly accessible system components are physically or logically separated from internal networks.

Assessors are instructed to-

Examine: [SELECT FROM: System and communications protection policy; procedures addressing boundary protection; system security plan; list of key internal boundaries of the system; system design documentation; boundary protection hardware and software; system configuration settings and associated documentation; enterprise security architecture documentation; system audit logs and records; other relevant documents or records].

Interview: [SELECT FROM: System or network administrators; personnel with information security responsibilities; system developer; personnel with boundary protection responsibilities].

Test: [SELECT FROM: Mechanisms implementing boundary protection capability].

FURTHER DISCUSSION

Separate the publicly accessible systems from the internal systems that need to be protected. Do not place internal systems on the same network as the publicly accessible systems and block access by default from DMZ networks to internal networks. One method of accomplishing this is to create a DMZ network, which enhances security by providing public access to a specific set of resources while preventing connections from those resources to the rest of the IT environment. Some OSAs achieve a similar result through the use of a cloud computing environment that is separated from the rest of the company’s infrastructure.

Example

The head of recruiting at your company wants to launch a website to post job openings and allow the public to download an application form [a]. After some discussion, your team realizes it needs to use a firewall to create a perimeter network to do this [b]. You host the server separately from the company’s internal network and make sure the network on which it resides is isolated with the proper firewall rules [b].

Potential Assessment Considerations

  • Are any system components reachable by the public (e.g., internet-facing web servers, VPN gateways, publicly accessible cloud services) [a]?

  • Are publicly accessible system components on physically or logically separated subnetworks (e.g., isolated subnetworks using separate, dedicated VLAN segments such as DMZs) [b]?

Frameworks & Controls