AC-7_unsuccessful-logon-attempts

AC-7 Unsuccessful Logon Attempts

High-Level Description

Family: Access Control (AC) Framework: NIST SP 800-53 Rev 5

The need to limit unsuccessful logon attempts and take subsequent action when the maximum number of attempts is exceeded applies regardless of whether the logon occurs via a local or network connection. Due to the potential for denial of service, automatic lockouts initiated by systems are usually temporary and automatically release after a predetermined, organization-defined time period. If a delay algorithm is selected, organizations may employ different algorithms for different components of the system based on the capabilities of those components. Responses to unsuccessful logon attempts may be implemented at the operating system and the application levels. Organization-defined actions that may be taken when the number of allowed consecutive invalid logon attempts is exceeded include prompting the user to answer a secret question in addition to the username and password, invoking a lockdown mode with limited user capabilities (instead of full lockout), allowing users to only logon from specified Internet Protocol (IP) addresses, requiring a CAPTCHA to prevent automated attacks, or applying user profiles such as location, time of day, IP address, device, or Media Access Control (MAC) address. If automatic system lockout or execution of a delay algorithm is not implemented in support of the availability objective, organizations consider a combination of other actions to help prevent brute force attacks. In addition to the above, organizations can prompt users to respond to a secret question before the number of allowed unsuccessful logon attempts is exceeded. Automatically unlocking an account after a specified period of time is generally not permitted. However, exceptions may be required based on operational mission or need.

What to Check

• Verify AC-7 Unsuccessful Logon Attempts is documented in SSP
• Validate all 2 control requirements are implemented
• Confirm control is operating effectively
• Review evidence of continuous monitoring for AC-7

How to Test

Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AC-7 implementation details. Verify the organization has documented how this control is satisfied.

Step 2: Validate Implementation

# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly

# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null

Step 3: Test Operating Effectiveness

Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.

Tools

Remediation Guide

Control Statement

Enforce a limit of [organization-defined] consecutive invalid logon attempts by a user during a [organization-defined] ; and Automatically [organization-defined] when the maximum number of unsuccessful attempts is exceeded.

Implementation Guidance

The need to limit unsuccessful logon attempts and take subsequent action when the maximum number of attempts is exceeded applies regardless of whether the logon occurs via a local or network connection. Due to the potential for denial of service, automatic lockouts initiated by systems are usually temporary and automatically release after a predetermined, organization-defined time period. If a delay algorithm is selected, organizations may employ different algorithms for different components of the system based on the capabilities of those components. Responses to unsuccessful logon attempts may be implemented at the operating system and the application levels. Organization-defined actions that may be taken when the number of allowed consecutive invalid logon attempts is exceeded include prompting the user to answer a secret question in addition to the username and password, invoking a lockdown mode with limited user capabilities (instead of full lockout), allowing users to only logon from specified Internet Protocol (IP) addresses, requiring a CAPTCHA to prevent automated attacks, or applying user profiles such as location, time of day, IP address, device, or Media Access Control (MAC) address. If automatic system lockout or execution of a delay algorithm is not implemented in support of the availability objective, organizations consider a combination of other actions to help prevent brute force attacks. In addition to the above, organizations can prompt users to respond to a secret question before the number of allowed unsuccessful logon attempts is exceeded. Automatically unlocking an account after a specified period of time is generally not permitted. However, exceptions may be required based on operational mission or need.

Risk Assessment

CWE Categories

References

• NIST SP 800-53 Rev 5 - AC-7
• NIST SP 800-53A Rev 5 (Assessment Procedures)
• NIST SP 800-53 Rev 5 Full Catalog

Checklist

• Control documented in SSP
• Implementation evidence collected
• Operating effectiveness validated
• Continuous monitoring in place
• Related controls (AC-2, AC-9, AU-2, AU-6, IA-5) reviewed