ERROR_NTLM_BLOCKED - 1937 (0x791)
Authentication failed because NTLM authentication has been disabled.
Updated: Feb 21, 2026
Technical Meaning
The ERROR_NTLM_BLOCKED error indicates that a Windows operation failed because NTLM (NT LAN Manager) authentication has been disabled. This error is typically encountered during the process of authenticating to a network resource or service.
Error Details
- Error Name: ERROR_NTLM_BLOCKED
- Numeric Code: 1937
- Hex Code: 0x791
- Short Description: Authentication failed because NTLM authentication has been disabled.
Usage Context
This error is relevant in scenarios where NTLM-based authentication mechanisms are required for access to network resources. It may occur when attempting to log into a domain, accessing shared files or printers, or using certain services that rely on NTLM for security.
Developer Interpretation
Developers should interpret this error as an indication that the system is configured to use alternative authentication methods (such as Kerberos) and not NTLM. This configuration might be due to security policies, network settings, or specific application requirements.
Related Errors
- ERROR_LOGON_FAILURE: Authentication failed for reasons other than NTLM being disabled.
- ERROR_INVALID_PARAMETER: A parameter passed during the authentication process was invalid.
- ERROR_ACCESS_DENIED: Access was denied based on current security context and policies.
FAQ
Q: Why is NTLM authentication disabled?
A: NTLM authentication might be disabled due to organizational security policies or network configurations that prioritize more secure authentication methods like Kerberos. Developers should consult relevant documentation or administrators for specific reasons.
Q: How can I resolve this error?
A: Ensure that the application or service is configured to use the appropriate authentication method as per the system's security settings. If NTLM must be used, verify that it has not been explicitly disabled and adjust the configuration accordingly.
Summary
The ERROR_NTLM_BLOCKED error signifies that NTLM-based authentication has been intentionally disabled on the system. Developers should understand this context when encountering this error to ensure proper handling of network authentication mechanisms in their applications.