NIST 800-171 3.1.1 (AC.L2-3.1.1): Authorized Access

What 3.1.1 means in practice

Every person, service and device that can reach the system has to be known in advance, and nothing else gets in. In practice that means an account inventory tied to named people, service accounts and managed identities with an owner, and a list of the devices allowed to connect. Accounts of people who have left are removed, and assessors test that by sampling recent departures.

SPRS points and the CMMC POA&M

What an assessor checks for 3.1.1

NIST SP 800-171A gives 6 determination statements for 3.1.1, each found satisfied or other than satisfied. Determine if:

1. 3.1.1[a] authorized users are identified.
2. 3.1.1[b] processes acting on behalf of authorized users are identified.
3. 3.1.1[c] devices (and other systems) authorized to connect to the system are identified.
4. 3.1.1[d] system access is limited to authorized users.
5. 3.1.1[e] system access is limited to processes acting on behalf of authorized users.
6. 3.1.1[f] system access is limited to authorized devices (including other systems).

NIST SP 800-171A (June 2018), assessment objectives for 3.1.1

Evidence that shows 3.1.1 is met

• A current list of active accounts with the person or owner behind each one, service accounts and managed identities included.
• Access request and approval records for a sample of recently created accounts.
• Records showing the accounts of people who left were disabled, matched against HR departure dates.
• The list of devices and systems allowed to connect, such as a device management enrollment report.
• Sign-in policy settings that turn away unknown users and devices.

How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.1.1 from it. Each line says what the product checks.

• Microsoft Entra ID: Conditional Access. Checks that Conditional Access policies restrict sign-in to the system to authorized users.
• AWS: IAM. Flags IAM user credentials that have not been used for 90 days.
• AWS: S3 buckets. Checks that each S3 bucket blocks public access and is neither publicly readable nor publicly writable.
• AWS: EC2 and VPC networking. Checks that running EC2 instances have no public IPv4 address, that subnets do not hand out public addresses, and that instances require IMDSv2.
• AWS: Data stores. Checks that RDS instances and Redshift clusters are not publicly accessible.
• AWS: Load balancers, API Gateway, CloudFront and Lambda. Checks that no Lambda function policy grants public access.