We have a multiple forest Exchange 2010 environment with roughly 20k mailboxes. Most of the users log into their workstations on a different forest, but all users log into Exchange with credentials in the Exchange forest.
What I am seeing is thousands of Event ID 4625 on my CAS/HUB Exchange 2010 servers. The user can be logged in to Outlook, Communicator, all appears fine to the user, but I will see 10-15 invalid login attempts per second from the users account. Here is one of the thousands:
An account failed to log on.Subject:
Security ID: NULL SID
Account Name: -
Account Domain:-
Logon ID: 0x0
Logon Type:3
Account For Which Logon Failed:
Security ID: NULL SID
Account Name: username removed
Account Domain:
Failure Information:
Failure Reason:Unknown user name or bad password.
Status: 0xc000006d
Sub Status: 0xc000006a
Process Information:
Caller Process ID:0x0
Caller Process Name:-
Network Information:
Workstation Name:removed
Source Network Address:10.23.23.23 (changed)
Source Port: 49347
Detailed Authentication Information:
Logon Process:NtLmSsp
Authentication Package:NTLM
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.
The frequency of these really vary but sometimes I'm seeing 100-200 events per second if I look at perfmon Events Logged Per Sec for Eventlog-Security.
Is this cause for concern or do I ignore these login failures?
Jason Meyer