Security Log

I see this quite often in my event log and feel that
someone is attempting to get into my servers/network.

When this happens, I notice that the account names are our
entire users accounts. Like this one started at 6:44:19
and had about 120 event ids 681 and 529. Each with the
different logon accounts.

The logon to account: administrator
by: MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
from workstation: AMSTERDA-R50NAC
failed. The error code was: 3221225578

They are all failed, but should I be concerned and is
there a way that I can track this guy/gal down? The
workstation changes not each time but each day. This
person has been attempting this for the past 4 weeks, with
no luck. All have failed.

Thanks