How To Prevent Auditable Activities When Security Log Is Full

Because the security log is limited in size, and because a large number of routine audit records can make it difficult to find records that suggest a security problem, you should carefully consider how you audit object access. Generating too many audit records require you to review and clear the security log more often that is practical.

WARNING: Using Registry Editor incorrectly can cause serious, system- wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

If you have set the security log either to "Overwrite Events Older than n Days" or "Do Not Overwrite Events (Clear Log Manually)", you may want to prevent auditable activities while the log is full so no new audit records can be written. To do this:

1. Run Registry Editor (REGEDT32.EXE).
2. From the HKEY_LOCAL_MACHINE\SYSTEM subtree, go to the following key:
   
   \CurrentControlSet\Control\Lsa\
3. Add the entry:
   
   Key: CrashOnAuditFail
   Type: REG_DWORD
   Value: 1
4. Save the changes. The Change will take effect the next time the computer is started. Update the Emergency Repair Disk to reflect these changes.

If Windows NT halts as a result of the security log becoming full, the system must be restarted and reconfigured to restore it to high-level security. When Windows NT restarts, the Security log is full and so no auditable actions are recorded until the Security log is cleared.

To recover when windows nt halts because it cannot generate an audit event record:

1. Restart the computer and log on using an account in the Administrators group.
2. Use Event Viewer to clear all events from the Security log, archiving the currently logged events. For details, see the "Event Viewer" chapter in the Windows NT Workstation or Windows NT Server System Guide.
3. Use the Registry Editor to delete and replace value entry CrashOnAuditFail, with data type REG_DWORD and value 1, under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa (as described above).
4. Exit and restart the computer.

NOTE: If the Security log reaches it's size limitation and causes a system halt, then the CrashOnAuditFail registry value is automatically changed from "0x1" to "0x2" to allow administrative logon to the system. The CrashOnAuditFail value must then be manually reset to 0x1 after the Security event log is cleared.