Audit Failure 4625 help

Hello,

I've recently started noticing these audit failures in our security log (typically about 500 or so a day) and am looking for a little "decryption" to assist in finding the root issue.

Log Name:      Security
Source:        Microsoft-Windows-Security-Auditing
Date:          7/15/2014 6:21:47 AM
Event ID:      4625
Task Category: Logon
Level:         Information
Keywords:      Audit Failure
User:          N/A
Computer:      SQL1.bel.local
Description:
An account failed to log on.

Subject:
Security ID: SYSTEM
Account Name: SQL1$
Account Domain:BEL
Logon ID: 0x3e7

Logon Type:10

Account For Which Logon Failed:
Security ID: NULL SID
Account Name: sofia
Account Domain:SQL1

Failure Information:
Failure Reason:Unknown user name or bad password.
Status: 0xc000006d
Sub Status: 0xc0000064

Process Information:
Caller Process ID:0x19d0
Caller Process Name:C:\Windows\System32\winlogon.exe

Network Information:
Workstation Name:SQL1
Source Network Address:64.20.54.226
Source Port: 57060

Detailed Authentication Information:
Logon Process:User32 
Authentication Package:Negotiate
Transited Services:-
Package Name (NTLM only):-
Key Length: 0

This event is generated when a logon request fails. It is generated on the computer where access was attempted.

The Subject fields indicate the account on the local system which requested the logon. This is most commonly a service such as the Server service, or a local process such as Winlogon.exe or Services.exe.

The Logon Type field indicates the kind of logon that was requested. The most common types are 2 (interactive) and 3 (network).

The Process Information fields indicate which account and process on the system requested the logon.

The Network Information fields indicate where a remote logon request originated. Workstation name is not always available and may be left blank in some cases.

The authentication information fields provide detailed information about this specific logon request.
- Transited services indicate which intermediate services have participated in this logon request.
- Package name indicates which sub-protocol was used among the NTLM protocols.
- Key length indicates the length of the generated session key. This will be 0 if no session key was requested.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" />
    <EventID>4625</EventID>
    <Version>0</Version>
    <Level>0</Level>
    <Task>12544</Task>
    <Opcode>0</Opcode>
    <Keywords>0x8010000000000000</Keywords>
    <TimeCreated SystemTime="2014-07-15T11:21:47.924057100Z" />
    <EventRecordID>11346952</EventRecordID>
    <Correlation />
    <Execution ProcessID="568" ThreadID="7620" />
    <Channel>Security</Channel>
    <Computer>SQL1.bel.local</Computer>
    <Security />
  </System>
  <EventData>
    <Data Name="SubjectUserSid">S-1-5-18</Data>
    <Data Name="SubjectUserName">SQL1$</Data>
    <Data Name="SubjectDomainName">BEL</Data>
    <Data Name="SubjectLogonId">0x3e7</Data>
    <Data Name="TargetUserSid">S-1-0-0</Data>
    <Data Name="TargetUserName">sofia</Data>
    <Data Name="TargetDomainName">SQL1</Data>
    <Data Name="Status">0xc000006d</Data>
    <Data Name="FailureReason">%%2313</Data>
    <Data Name="SubStatus">0xc0000064</Data>
    <Data Name="LogonType">10</Data>
    <Data Name="LogonProcessName">User32 </Data>
    <Data Name="AuthenticationPackageName">Negotiate</Data>
    <Data Name="WorkstationName">SQL1</Data>
    <Data Name="TransmittedServices">-</Data>
    <Data Name="LmPackageName">-</Data>
    <Data Name="KeyLength">0</Data>
    <Data Name="ProcessId">0x19d0</Data>
    <Data Name="ProcessName">C:\Windows\System32\winlogon.exe</Data>
    <Data Name="IpAddress">64.20.54.226</Data>
    <Data Name="IpPort">57060</Data>
  </EventData>
</Event>