Users cannot access Web sites when the security event log is full

When you access a Web site on the server, you receive one of the following error messages.When friendly error messages are turned off in the browser, you may also receive the following error message:

This problem occurs if the security event log has reached the maximum log size and the Event Log Wrapping setting is set to Overwrite Events Older than X Days or Do Not Overwrite Events. Because the security event log is full, and the CrashOnAuditFail registry key is set, Microsoft Windows does not permit accounts that are not administrator accounts to log on. When anonymous access is configured, requests to the Web site try to authenticate by using the IUSR_computername and IWAM_computername accounts. These accounts are not administrator accounts.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

To resolve this issue, follow these steps:

1. Save and clear the security event log.
2. Start Registry Editor.
3. Locate the following key, and then set the value of this key to 1:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\CrashOnAuditFail
4. Restart the server. The registry changes do not take effect until you restart the server.

This behavior is by design.

The CrashOnAuditFail registry key provides an optional security feature that system administrators can use to review all security events. The valid values for the CrashOnAuditFail key are 0, 1, and 2. The data options are:

• 0 - Anyone may log on. This is the default value.
• 1 - Anyone may log on if the system can audit the events and write the events to the security event log. If the security event log is full, the value for the CrashOnAuditFail key is changed to 2, and the server crashes.
• 2 - Only administrators may log on.

When the security event log becomes full, the server locks itself down so that no auditable events are missed. You can prevent the server lockdown by using one of the following methods. Note, however, that preventing the server lockdown defeats the purpose of the CrashOnAuditFail key.

Note None of the following methods alone resolves the issue. You must follow the steps in the "Resolution" section before you use one of these methods.

• Set the Event Log Wrapping setting to Overwrite events as needed.
• Limit the number or types of events that are audited, or disable auditing completely.
• Set the value for the following registry key to 0:
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\CrashOnAuditFail

For additional information about using the CrashOnAuditFail security feature, click the following article numbers to view the articles in the Microsoft Knowledge Base: