Disabling Kerberos Preauthentication

The Active Directory KDC enables Kerberos preauthentication and I keep getting the event "Pre-authentication Failed - outside work hours 675” to my centralized events manager every time a user login.
Pre-authentication failed:
      User Name:      UserX
      User ID:            TULSA\UserX
      Service Name:      krbtgt/DomainName
      Pre-Authentication Type:      0x0
      Failure Code:      0x19
Client Address:      192.168.1.X

Pre-authentication failed:
      User Name:      UserX
      User ID:            Domain/UserX
      Service Name:      krbtgt/Domain
      Pre-Authentication Type:      0x2
      Failure Code:      0x18
Client Address:      192.168.1.X

I noticed that there are two error codes 0x19 and 0x18 and two preauthenticatio types: 0x0 and 0x2. What is the difference these two events? How can I stop them?

Are there any security risks behind disabling Kerberos Preauthentication on user accounts?

 Please help me solve this issue.


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Mike KlineConnect With a Mentor Commented:
Download this whitepaper about troubleshooting kerberos that lists a lot of the events   http://www.microsoft.com/downloads/en/details.aspx?FamilyID=7DFEB015-6043-47DB-8238-DC7AF89C93F1&displaylang=en

Looks like a bad password

AbdellahTAuthor Commented:
Thanks for your reply.

What's a bad password?
danoraConnect With a Mentor Commented:
Hi AbdellahT

Event 675 is a locked account.

Please see the below link for a more comprehensive answer


Hope this helps
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DigitalTechyConnect With a Mentor Commented:
I'm assuming you are in a windows 2003 environment?  Regardless a mix-match of OS's in older domain controllers can't cause the 0x19 failure.  Microsoft cycles through the encryption type and if it doesn't match up it goes on to the next to support various versions.  This is by design and is not to cause alarm, however, it does produce multiple 0x19 failures.  In order to no longer receive them you must disable the kerberos authentication logging.  

On another note, the 0x18 error code means Account disabled, expired or locked out.  If it is in unison (via timestamp) to the 0x19's it's probably caused by the kerberos encryption.  If it's not then I'd take a look at if that user is locked out or if the trust relationship between the workstation and server is out of sync.  I've seen this numerous times, if the user is able to successfully authenticate yet you still get multiple 0x18 675 errors, you may just have to remove them from the domain and re-add them.  Problem shouldn't re-occur.  

In any case, here is more information on the pre-auth encryption and steps on how to disable if you choose to do so.  I'd rather recommend if you have security monitoring software to write a custom query to skip alerting on 0x19 if needed in your environment. 0x18 is still useful.

Event 675 is not just a bad password it can be, you have to look deeper at the actual status codes, logon types, ntlm error codes or whatever else you have available in the logs.  I'll attach a quickref guide for you.

Event 675 on a domain controller indicates a
failed initial attempt to logon via Kerberos at a
workstation with a domain account usually due
to a bad password but the failure code indicates
exactly why authentication failed. See Kerberos
failure codes quickref.pdf
AbdellahTAuthor Commented:
When you guys say Bad Password, do you mean is when a user failed to type the correct password? usually users mistype their password in the first login attempt, is then when this error is thrown?

AwinishConnect With a Mentor Commented:
Bad password are the wrong password entered by user or tried by virus/worm to enter to the system for stealing information from the system
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