Logon Failure Event

Hello folks,

Last couple of days, I started getting a lot of logon failure events on one of the servers. The Source Network Addresses are from the LAN. Here is the error:

Logon Failure:
Reason: Unknown user name or bad password
User Name:
Domain:
Logon Type: 3
Logon Process: Kerberos
Authentication Package: Kerberos
Workstation Name: -
Caller User Name: -
Caller Domain: -
Caller Logon ID: -
Caller Process ID: -
Transited Services: -
Source Network Address: 192.168.x.x
Source Port: 0

Any help would be appreciated.