The NIST SP 800-53 Revision 5 outlines essential guidelines for protecting information systems. One of its core components, the Access Control (AC) family, consists of 23 specific controls designed to help organizations manage who can access critical systems, how they gain access, and under what circumstances. Each control addresses a unique aspect of access management, from user account management to advanced security requirements, creating a comprehensive security framework.
In this guide, we’ll break down all 23 AC controls in NIST SP 800-53 Rev 5. By understanding these controls, organizations can create a more secure environment, enhance data privacy, and achieve compliance.
Introduction to Access Control (AC) in NIST SP 800-53 Rev 5
Access control ensures that only authorized individuals can access certain systems and data. The NIST SP 800-53 Rev 5 AC family includes 23 controls, each addressing a different aspect of access management. Together, they form a robust framework that helps organizations limit access to sensitive data and manage who can perform specific actions within systems. There are 25 controls listed for reference, including two controls that have been deprecated in Rev 5 from Rev 4.
Let’s explore each AC control in detail to understand its purpose, implementation steps, and benefits.
1. AC-1: Access Control Policy and Procedures
AC-1 establishes the need for an organization-wide access control policy and accompanying procedures.
- Purpose: Provides a foundation for all other access controls.
- Implementation: Develop, document, and distribute the policy. Review it periodically and update as necessary.
This control ensures that organizations have a clear strategy to manage access control effectively.
2. AC-2: Account Management
AC-2 requires organizations to manage user accounts, including account creation, modification, and termination.
- Purpose: Controls user access to information systems.
- Implementation: Set account roles, periodically review accounts, and remove or deactivate unused ones.
Effective account management reduces the risk of unauthorized access.
3. AC-3: Access Enforcement
AC-3 focuses on enforcing access control policies to ensure that access restrictions are properly implemented.
- Purpose: Ensures users can access only what they’re authorized to.
- Implementation: Use mechanisms like role-based access control to restrict access.
Proper access enforcement keeps sensitive data safe.
4. AC-4: Information Flow Enforcement
This control ensures that information within systems flows only between authorized components.
- Purpose: Prevents unauthorized data flow between systems or networks.
- Implementation: Use firewalls, data loss prevention tools, or network segmentation.
Information flow enforcement minimizes data leakage risks.
5. AC-5: Separation of Duties
AC-5 ensures no single user has complete control over critical tasks, reducing the risk of fraud.
- Purpose: Prevents conflicts of interest.
- Implementation: Split responsibilities among different users.
Separation of duties adds a layer of accountability.
6. AC-6: Least Privilege
AC-6 requires that users have only the minimum level of access necessary to perform their roles.
- Purpose: Reduces potential damage from insider threats.
- Implementation: Regularly review and adjust privileges based on job roles.
Implementing least privilege limits users’ access to sensitive data.
7. AC-7: Unsuccessful Logon Attempts
AC-7 controls the number of failed login attempts to prevent unauthorized access.
- Purpose: Protects systems from brute force attacks.
- Implementation: Lock accounts after a set number of failed attempts.
By limiting failed logins, this control thwarts unauthorized access attempts.
8. AC-8: System Use Notification
This control mandates that users are notified about the system’s usage policies each time they log in.
- Purpose: Ensures users understand the acceptable use policy.
- Implementation: Display a banner or message at logon.
Clear system use notifications set expectations for proper use.
9. AC-9: Previous Logon Notification
AC-9 informs users about previous logon details, allowing them to spot any unauthorized activity.
- Purpose: Helps users detect suspicious account activity.
- Implementation: Display the last logon time on the login page.
Notifying users of previous logins promotes account security.
10. AC-10: Concurrent Session Control
Limits the number of active sessions a user can have.
- Purpose: Prevents excessive resource usage and potential abuse.
- Implementation: Set session limits based on role requirements.
Concurrent session control safeguards system resources.
11. AC-11: Session Lock
Requires automatic session locking after a period of inactivity.
- Purpose: Prevents unauthorized access when users leave sessions open.
- Implementation: Use automatic session locks on all systems.
Session locks protect systems from unauthorized use.
12. AC-12: Session Termination
Ensures that sessions are automatically terminated after a set period.
- Purpose: Limits exposure to unauthorized access.
- Implementation: Set time limits for inactive sessions.
Session termination reduces risk from unattended sessions.
13. AC-13: Supervision and Review of Information System Access*
AC-13 focused on the monitoring and review of access activities to detect misuse in Rev 4. It has been incorporated into AC-2 AND AU-6 in Rev 5.
- Purpose: Identifies and addresses suspicious access behavior.
- Implementation: Conduct regular audits and review access logs.
Regular reviews catch unauthorized access early.
14. AC-14: Permitted Actions Without Identification or Authentication
Specifies actions users can perform without logging in, like viewing a public webpage.
- Purpose: Clarifies access expectations.
- Implementation: Document actions permitted without authentication.
Clear guidelines help manage anonymous access.
15. AC-15: Automated Marking*
Ensured sensitive data is labeled based on classification levels in Rev 4. It has been incorporated into MP-3 in Rev 5.
- Purpose: Aids in protecting sensitive data.
- Implementation: Use automated tools to label information.
Data labeling supports data privacy efforts.
16. AC-16: Security Attributes
Defines specific attributes or permissions for users, files, or data.
- Purpose: Allows for granular access control.
- Implementation: Set permissions based on attributes.
Customizable security attributes enhance access management.
17. AC-17: Remote Access
Controls how users can remotely access the organization’s systems.
- Purpose: Secures remote access points.
- Implementation: Use secure VPNs and enforce multi-factor authentication.
Strong remote access policies prevent unauthorized connections.
18. AC-18: Wireless Access
Regulates access to wireless networks to prevent unauthorized use.
- Purpose: Secures wireless networks.
- Implementation: Use WPA2 or WPA3 encryption for wireless access.
Secure wireless access protects against local threats.
19. AC-19: Access Control for Mobile Devices
Restricts access based on mobile device use, such as tablets or smartphones.
- Purpose: Mitigates risks from mobile device access.
- Implementation: Enforce policies for device security.
Proper mobile device access limits exposure to threats.
20. AC-20: Use of External Information Systems
Controls access when using systems outside of the organization’s control.
- Purpose: Limits exposure to unmanaged systems.
- Implementation: Restrict external access or use encrypted connections.
Managing external access reduces third-party risks.
21. AC-21: Information Sharing
Sets controls for data sharing across systems or with external entities.
- Purpose: Protects shared information.
- Implementation: Use encryption and establish sharing protocols.
Controlled information sharing secures data in transit.
22. AC-22: Publicly Accessible Content
Ensures only authorized content is publicly accessible, like public webpages.
- Purpose: Restricts public access to sensitive data.
- Implementation: Limit public access and review content regularly.
Securing public content prevents accidental data leaks.
23. AC-23: Data Integrity and Availability Controls
Protects data by ensuring integrity and availability even during disruptions.
- Purpose: Prevents unauthorized alterations to data.
- Implementation: Implement redundancy and integrity checks.
Data integrity controls ensure reliable access.
24. AC-24: Access Control for Program Execution
Prevents unauthorized programs from running on the network.
- Purpose: Reduces risk of malware or unauthorized apps.
- Implementation: Whitelist authorized software.
Program control safeguards against malicious software.
25. AC-25: Account Management Policies
Requires policies to manage and review user accounts.
- Purpose: Ensures accounts are managed responsibly.
- Implementation: Define policies for account use, including termination.
Clear account policies maintain security standards.
Conclusion: Strengthening Access Control with NIST SP 800-53 Rev 5
Each control in the NIST SP 800-53 Rev 5 Access Control family plays a role in creating a secure information environment. By following these guidelines, organizations can better manage access to critical systems and data, ultimately enhancing their cybersecurity posture.