SI-14 Non-persistence

Guidance: nonePolicy clause: noneWhat these mean

Baselines	Implementation level	Enhancements
Not in a baseline	Organization	3 (0 in a baseline)

Related controls: SC-30, SC-34, SI-21

Control statement

Implement non-persistent [Assignment: organization-defined system components and services] that are initiated in a known state and terminated [Selection (one or more): upon end of session of use; [Assignment: organization-defined frequency] ].

NIST discussion

Implementation of non-persistent components and services mitigates risk from advanced persistent threats (APTs) by reducing the targeting capability of adversaries (i.e., window of opportunity and available attack surface) to initiate and complete attacks. By implementing the concept of non-persistence for selected system components, organizations can provide a trusted, known state computing resource for a specific time period that does not give adversaries sufficient time to exploit vulnerabilities in organizational systems or operating environments. Since the APT is a high-end, sophisticated threat with regard to capability, intent, and targeting, organizations assume that over an extended period, a percentage of attacks will be successful. Non-persistent system components and services are activated as required using protected information and terminated periodically or at the end of sessions. Non-persistence increases the work factor of adversaries attempting to compromise or breach organizational systems.

Non-persistence can be achieved by refreshing system components, periodically reimaging components, or using a variety of common virtualization techniques. Non-persistent services can be implemented by using virtualization techniques as part of virtual machines or as new instances of processes on physical machines (either persistent or non-persistent). The benefit of periodic refreshes of system components and services is that it does not require organizations to first determine whether compromises of components or services have occurred (something that may often be difficult to determine). The refresh of selected system components and services occurs with sufficient frequency to prevent the spread or intended impact of attacks, but not with such frequency that it makes the system unstable. Refreshes of critical components and services may be done periodically to hinder the ability of adversaries to exploit optimum windows of vulnerabilities.

Control enhancements

SI-14(1) Refresh from Trusted Sources

Baselines: Not in a baseline

Obtain software and data employed during system component and service refreshes from the following trusted sources: [Assignment: organization-defined trusted sources].

Discussion and assessment objectives for SI-14(1)

Trusted sources include software and data from write-once, read-only media or from selected offline secure storage facilities.

Determine if the software and data employed during system component and service refreshes are obtained from [Assignment: organization-defined trusted sources].

Examine: System and information integrity policy; system and information integrity procedures; procedures addressing non-persistence for system components; system design documentation; system configuration settings and associated documentation; system audit records; system security plan; other relevant documents or records.

Interview: Organizational personnel responsible for obtaining component and service refreshes from trusted sources; organizational personnel with information security responsibilities.

Test: Organizational processes for defining and obtaining component and service refreshes from trusted sources; automated mechanisms supporting and/or implementing component and service refreshes.

SI-14(2) Non-persistent Information

Baselines: Not in a baseline

(a) [Selection: refresh [Assignment: organization-defined information] [Assignment: organization-defined frequency] ; generate [Assignment: organization-defined information] on demand] ; and
(b) Delete information when no longer needed.

Discussion and assessment objectives for SI-14(2)

Retaining information longer than is needed makes the information a potential target for advanced adversaries searching for high value assets to compromise through unauthorized disclosure, unauthorized modification, or exfiltration. For system-related information, unnecessary retention provides advanced adversaries information that can assist in their reconnaissance and lateral movement through the system.

Determine if:

SI-14(02)(a) [Selection: refresh [Assignment: organization-defined information] [Assignment: organization-defined frequency] ; generate [Assignment: organization-defined information] on demand] is performed;
SI-14(02)(b) information is deleted when no longer needed.

Interview: Organizational personnel responsible for ensuring that information is and remains non-persistent; organizational personnel with information security responsibilities.

Test: Organizational processes for ensuring that information is and remains non-persistent; automated mechanisms supporting and/or implementing component and service refreshes.

SI-14(3) Non-persistent Connectivity

Baselines: Not in a baseline

Establish connections to the system on demand and terminate connections after [Selection: completion of a request; a period of non-use].

Discussion and assessment objectives for SI-14(3)

Persistent connections to systems can provide advanced adversaries with paths to move laterally through systems and potentially position themselves closer to high value assets. Limiting the availability of such connections impedes the adversary’s ability to move freely through organizational systems.

Determine if:

SI-14(03)[01] connections to the system are established on demand;
SI-14(03)[02] connections to the system are terminated after [Selection: completion of a request; a period of non-use].

Interview: Organizational personnel responsible for limiting persistent connections; organizational personnel with information security responsibilities.

Test: Organizational processes for limiting persistent connections; automated mechanisms supporting and/or implementing non-persistent connectivity.

Assessment objectives (SP 800-53A)

Objectives and methods for SI-14

Determine if:

SI-14[01] non-persistent [Assignment: organization-defined system components and services] that are initiated in a known state are implemented;
SI-14[02] non-persistent [Assignment: organization-defined system components and services] are terminated [Selection (one or more): upon end of session of use; [Assignment: organization-defined frequency] ].

Interview: Organizational personnel responsible for non-persistence; organizational personnel with information security responsibilities; system/network administrators; system developer.

Test: Automated mechanisms supporting and/or implementing the initiation and termination of non-persistent components.

Independent guidance, not an official NIST publication. Control text is from NIST SP 800-53 Rev. 5 and SP 800-53A (public domain). Original content is licensed CC BY 4.0; program templates and the downloadable kit are dedicated to the public domain under CC0 1.0.