As of this morning we have had thousands of failed login attempts to our SQL Server 2012 box.
Login failed for user 'Domain\User'. Reason: Infrastructure error occurred.
Check for previous errors. [CLIENT: 10.xxx.xxx.xxx]
I have checked all the logs, permissions, and scoured forums for help on this issue but to no avail.
Server Login & Database User accounts are enabled
Server Login is mapped to the database that it has access too
Windows & SQL Server Authentication is applied
SA account is enabled
No orphaned users
Any ideas ?