NET-39.3: Authenticated Received Chain (ARC)
Mechanisms exist to utilize an authenticated received chain that allows for an intermediary to sign its own authentication of the original email, allowing downstream entities to accept the intermediary's authentication even if the email was changed.
Renumbered: Formerly NET-20.3 in SCF 2025.4.
Control Question: Does the organization utilize an authenticated received chain that allows for an intermediary to sign its own authentication of the original email, allowing downstream entities to accept the intermediary's authentication even if the email was changed?
US (1)
| Framework | Mapping Values |
|---|---|
| USA Federal DHS CISA TIC 3.0 | 3.PEP.EM.ARCHA |
Capability Maturity Model
Level 0 — Not Performed
Practices are non-existent, based on the inability to demonstrate an implemented and operational capability. A reasonable person would conclude the control is not being performed.
Level 1 — Performed Informally
SCR-CMM Level 1 criteria definitions are not available for this control: ▪ A reasonable person would conclude this control requires a structured process. ▪ At this level of maturity, the "ad hoc" nature of performing a capability informally would indicate the intent of the control is not met due to a lack of consistency and formality.
Level 2 — Planned & Tracked
SCR-CMM Level 2 criteria definitions are not available for this control: ▪ A reasonable person would conclude a well-defined and standardized process is required. ▪ At this level of maturity, the “requirements-driven” nature of performing the control is focused on a localized and/or regionalized implementation, not uniform and consistent across the organization. ▪ Requirements are narrowly scoped for applicability and are primarily derived from compliance obligations (e.g., laws, regulations and contracts).
Level 3 — Well Defined
Network Security (NET) capabilities are standardized across the entity for applicability to People, Processes, Technologies, Data and/or Facilities (PPTDF) to ensure consistency for Technology Assets, Applications, Services and/or Data (TAASD). Capability criteria associated with this control reasonably expect the following criteria to exist: ▪ Policies and standards associated with NET domain capabilities are formally documented and centrally-managed by the entity's Governance, Risk & Compliance (GRC) team, or similar function. ▪ Standardized Operating Procedures (SOP) associated with NET domain capabilities are well-documented and kept current by process owners. ▪ A network security management team, or similar function, is appropriately staffed and supported to implement and maintain NET domain capabilities. ▪ Technology is leveraged to enhance the efficiency and accuracy of network security operations (e.g., network management solution and log aggregator). ▪ The entity's Governance, Risk & Compliance (GRC) team, or similar function, works with business stakeholders and process owners to appropriately scope and reasonably implement cybersecurity and data protection controls associated with NET domain capabilities to address Minimum Compliance Requirements (MCR) (e.g., applicable statutory, regulatory and/or contractual requirements) and Discretionary Security Requirements (DSR) (e.g., entity-required controls). ▪ Secure Baseline Configurations (SBC) enforce the principles of least privileges and least functionality for boundary protection technologies. ▪ An implemented and operational capability exists to utilize an authenticated received chain that allows for an intermediary to sign its own authentication of the original email, allowing downstream entities to accept the intermediary's authentication even if the email was changed.
Level 4 — Quantitatively Controlled
Utilize SCR-CMM Level 3 criteria definitions: ▪ There are no defined Level 4 criteria, since it is reasonable to assume a quantitatively-controlled process is not necessary to operationalize this control. ▪ While it may be possible to develop “metrics-driven” capabilities for this control, the criteria would be organization-specific to define.
Level 5 — Continuously Improving
Utilize SCR-CMM Level 3 or Level 4 (if available) criteria definitions: ▪ There are no defined Level 5 criteria, since it is reasonable to assume a continuously-improving process is not necessary to operationalize this control. ▪ Level 5 capabilities should be considered “world-class” where the control builds on Level 4 capabilities, but are continuously improving through Artificial Intelligence (AI) and/or Machine Learning (ML) technologies. ▪ While it may be possible to develop responsive capabilities for this control through the use of AI and/or ML technologies, the criteria would be organization-specific to define.
Assessment Objectives
- NET-39.3_A01 email systems are configured to utilize an Authenticated Received Chain (ARC) that allows an intermediary to sign its own authentication of the original email, allowing downstream entities to accept the intermediary’s authentication even if the email was changed.
Evidence Requirements
- E-NET-12 Email Security Configuration
-
Documented evidence of email domain reputation protections (DMARC, SPF, ARC) and phishing / spam protection configurations.
Network Security
Technology Recommendations
Micro/Small
- Note: Typically not required at this size; ARC provided by email service (e.g., Microsoft 365, Google Workspace)
Small
- ARC handled by hosted email platform (Microsoft 365 / Google Workspace); verify enabled
Medium
- Implement ARC for email forwarding authentication chains
Large
- Enterprise email platform with ARC support (e.g., Microsoft Exchange Online)
Enterprise
- Enterprise email platform with full ARC implementation
- Monitoring of ARC chain failures