Mysterious Failed Login Attempts on a server

Within the last month, my server has had several failed login attempts on two nights.  We have had login attempts in the past, but they always give us a source IP address to trace the origin of the attack.  This latest round however, there is no source IP address.  The attacks happened on 3/6 and 3/21, all overnight and over the span of one hour.

This is one of the logs we have:
Event Type:      Failure Audit
Event Source:      Security
Event Category:      Logon/Logoff
Event ID:      529
Date:            3/23/2010
Time:            1:27:36 PM
User:            NT AUTHORITY\SYSTEM
Computer:      BOSS
Logon Failure:
       Reason:            Unknown user name or bad password
       User Name:      admin
       Logon Type:      3
       Logon Process:      Advapi  
       Authentication Package:      MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
       Workstation Name:      BOSS
       Caller User Name:      BOSS$
       Caller Domain:      RC
       Caller Logon ID:      (0x0,0x3E7)
       Caller Process ID:      2312
       Transited Services:      -
       Source Network Address:      -
       Source Port:      -

The process ID does show up on our server as INETINFO.EXE.  

Could they hacking IIS or is there something else I can do to lock them out.


StewartTechnologiesIT ConsultantAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Rob WilliamsCommented:

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.