Ive had this critical error in my SBS security log. Its repeated 69 times. I have the same error on my server at home too.
What should I do 
Logon Failure:
Reason: Unknown user name or bad password
User Name: Administrator
Domain:
Logon Type: 10
Logon Process: User32
Authentication Package: Negotiate
Workstation Name: *************
Caller User Name: ************
Caller Domain: ***********
Caller Logon ID: (0x0,0x3E7)
Caller Process ID: 6068
Transited Services: -
Source Network Address: 66.111.11.181
Source Port: 61831