How do I find source of account lockouts - event messages have spoofed machine names

Two or three times a day essentially all of my users are getting their account locked out. I suspect someone on my network has a virus that is trying to brute force passwords on my users. The trouble I am having is identifying the machine(s) that are involved in this. They are somehow spoofing the machine name so the security event shows a NetBIOS name that does not exist in my network.

I am running primarily Windows 7 workstations and laptops; and Windows 2008 R2 servers and domain controllers.

Any guidance on how to locate the source of this chaos will be much appreciated!
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bgoeringAsked:
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arnoldCommented:
Get the lockout tool from the link, http://www.microsoft.com/en-us/download/details.aspx?id=18465

It includes/ids the DC that locked the account, then searching for the security events 4096 I think event on the referenced DC, it will include the source of the request using the event search tool included with the tool.
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arnoldCommented:
The event id referenced might not be right,

Here is a ref what you need to do with the tool included...

Here is a link where it explains things http://social.technet.microsoft.com/wiki/contents/articles/4585.account-locked-out-troubleshooting-eventcombmt.aspx
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Muhammad BurhanManager I.T.Commented:
Have you tried Advance Audit Policy ?Audi_Lockout2.jpgAudi_Lockout.jpg
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John TsioumprisSoftware & Systems EngineerCommented:
Netwrix account lockout examiner is free and gives plenty of information to nail down the problem...I had a Conflicker infection a couple a years ago and i managed to find the workstation which was causing this havoc with the help of this tool...
You can get it here
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bgoeringAuthor Commented:
Thanks everyone for the input.

John, I am already running the (free version of) Netwrix ALE and it is less than useful at locating offending devices when the workstation name is spoofed or blank.

Muhammed - I have not set up the advanced auditing, but will look into that.

Arnold - The EventCombMT tool helped to narrow it down. It turned out that one of the firewall administrators had left our disaster recovery site essentially open to the Internet - and everyone was having fun.

Lockouts went away after closing the firewall. Will be having folks checking equipment there for any hint of a compromise.

Thanks again
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