Authorized Access Control
Assessment Objectives [NIST SP 800-171A]
[a] authorized users are identified;
[b] processes acting on behalf of authorized users are identified;
[c] devices (and other systems) authorized to connect to the system are identified;
[d] system access is limited to authorized users;
[e] system access is limited to processes acting on behalf of authorized users; and
[f] system access is limited to authorized devices (including other systems).
Potential Assessment Methods and Objects [NIST SP 800-171A]
[SELECT FROM: Access control policy; procedures addressing account management; system security plan; system design documentation; system configuration settings and associated documentation; list of active system accounts and the name of the individual associated with each account; notifications or records of recently transferred, separated, or terminated employees; list of conditions for group and role membership; list of recently disabled system accounts along with the name of the individual associated with each account; access authorization records; account management compliance reviews; system monitoring records; system audit logs and records; list of devices and systems authorized to connect to organizational systems; other relevant documents or records].
[SELECT FROM: Personnel with account management responsibilities; system or network administrators; personnel with information security responsibilities].
[SELECT FROM: Organizational processes for managing system accounts; mechanisms for implementing account management].
Discussion [NIST SP 800-171 R2]
Access control policies (e.g., identity- or role-based policies, control matrices, and cryptography) control access between active entities or subjects (i.e., users or processes acting on behalf of users) and passive entities or objects (e.g., devices, files, records, and domains) in systems. Access enforcement mechanisms can be employed at the application and service level to provide increased information security. Other systems include systems internal and external to the organization. This requirement focuses on account management for systems and applications. The definition of and enforcement of access authorizations, other than those determined by account type (e.g., privileged verses [sic] non-privileged) are addressed in requirement 3.1.2 (AC.L1-3.1.2).
Identify users, processes, and devices that are allowed to use company computers and can log on to the company network. Automated updates and other automatic processes should be associated with the user who initiated (authorized) the process. Limit the devices (e.g., printers) that can be accessed by company computers. Set up your system so that only authorized users, processes, and devices can access the company network.
This practice, AC.L1-3.1.1, controls system access based on user, process, or device identity. AC.L1-3.1.1 leverages IA.L1-3.5.1 which provides a vetted and trusted identity for access control.
Your company maintains a list of all personnel authorized to use company information systems [a]. This list is used to support identification and authentication activities conducted by IT when authorizing access to systems [a,d].
A coworker wants to buy a new multi-function printer/scanner/fax device and make it available on the company network. You explain that the company controls system and device access to the network and will prevent network access by unauthorized systems and devices [c]. You help the coworker submit a ticket that asks for the printer to be granted access to the network, and appropriate leadership approves the device [f].
Potential Assessment Considerations
- Is a list of authorized users maintained that defines their identities and roles [a]?
- Are account requests authorized before system access is granted [d,e,f]?
The main goal of AC.L1-3.1.1 is to ensure that all users, processes, and devices accessing your information system are identified, and that access is limited to only those identified users, processes, and devices.
To identify a user or device, you should have a process by which authorized users/processes/devices are authorized. For example:
Example: User Authorization [a]
The user requests access to the information system, which is approved by their manager as needed. HR performs a background check, after which their access status is recorded in the CMDB. IT then provisions the employee's accounts in Active Directory and onboards the user.
Example: Limiting to Authorized Users [d]
IT validates that all active accounts in the system are authorized against the CMDB.
Example: Processes Acting on Behalf of a User Authorization [b]
An employee needs a process account in order to run some background tasks. They submit a request to IT providing details of this need, and their manager approves the request. IT provisions the account in Active Directory, recording the account's owner and purpose in the CMDB.
Example: Limiting to Authorized Processes [e]
IT regularly validates that all process accounts have a legitimate owner and purpose.
Example: Device Authorization [c]
A new employee arrives for their first day of work. IT takes a computer from inventory and marks in the CMDB that they are providing it to the employee.
Example: Limiting to Authorized Devices [f]
IT configures all laptops to be joined to their company domain. IT also configures all network access to be limited to only domain-joined devices. IT validates that there are no unidentified devices accessing the system.