# SC-21 Secure Name/Address Resolution Service (Recursive or Caching Resolver) — NIST 800-53 Rev5 control

> FedRAMP Consolidated Rules for 2026 v2026.07.14.01 · updated 2026-07-14
> Canonical page: /control/sc-21

Canonical id: `sc-21` · family `SC`

> Request and perform data origin authentication and data integrity verification on the name/address resolution responses the system receives from authoritative sources.

_Control title and statement: NIST SP 800-53 Rev5 catalog (the pinned commit is in `/api` under `control_text`). The FedRAMP rules reference these controls by id only; everything below is what FedRAMP says about this id._

## Rev5 baseline membership

- certification class B (in the annual independent assessment)
- certification class C (in the annual independent assessment)
- certification class D (in the annual independent assessment)

## Key Security Indicators that reach it

- `KSI-IAM-ELP` — Ensuring Least Privilege (Identity and Access Management)
  Identity and access management measures are used and persistently reviewed to ensure each user or device can only access the resources they need.
- `KSI-SVC-SIN` — Securing Information (Service Configuration)
  Information is encrypted or otherwise secured from unwanted access or modification.

## FedRAMP guidance

_No FedRAMP-specific guidance attaches to this control._

## Annual independent assessment

In the annual assessment subset for class B, C, D.