Failed login attempt from domain controller

[I_NeedHelp_Now]

Hello,
I'm seeing event codes 675 with failure code 0x18 in my security logs on my domain controllers. I am trying to track down the cause, but the client address listed in the event log is that of the domain controller. Any ideas?????

 

[Cyberat_88]

Get router logs for a first, this will alert you if any intrusions. Second, firewall logs. Cross reference them.