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On Windows Server 2008 R2 Standard ED. We have tons of ANONYMOUS LOGON logged under Event Viewer

How to stop this ? How to disable ANONYMOUS LOGON ?

Copy of messagge:


An account was successfully logged on.

Subject:
    Security ID:        NULL SID
    Account Name:       -
    Account Domain:     -
    Logon ID:       0x0

Logon Type:         3

New Logon:
    Security ID:        ANONYMOUS LOGON
    Account Name:       ANONYMOUS LOGON
    Account Domain:     NT AUTHORITY
    Logon ID:       0x7863af9a
    Logon GUID:     {00000000-0000-0000-0000-000000000000}

Process Information:
    Process ID:     0x0
    Process Name:       -

Network Information:
    Workstation Name:   ZZC-01309261645
    Source Network Address: 111.xxx.xxx.134
    Source Port:        55xxx

Detailed Authentication Information:
    Logon Process:      NtLmSsp 
    Authentication Package: NTLM
    Transited Services: -
    Package Name (NTLM only):   NTLM V1
    Key Length:     128

This event is generated when a logon session is created. It is generated on the computer that was accessed.

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 occurred. The most common types are 2 (interactive) and 3 (network).

The New Logon fields indicate the account for whom the new logon was created, i.e. the account that was logged on.

The network 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.
    - Logon GUID is a unique identifier that can be used to correlate this event with a KDC event.
    - 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.
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1 Answer 1

You can use a registry key to restrict it

HKEY_LOCAL_MACHINE\SYSTEM\CurrentcontrolSet\Control\Lsa

Change DWORD “RestrictAnonymous” to value 2

This will set it to level 2 restriction. Be careful, though, as it can break things, as seen here with problems associated with Windows 2000.

http://support.microsoft.com/default.aspx?scid=KB;en-us;296405

You may want to take some additional looks into your machine, and possibly your network, though. You've got NTLM running which is a very old and very insecure protocol called NT Lan Manager. You've also possibly got open ports where there shouldn't be, indicating that you may not be protected by a firewall. Windows security has improved over the years, but its still dangerous to be running "naked" on the Internet, especially when you've got NTLM happening. Get that thing behind a firewall, and perhaps look into having a security pro look into your configuration.

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just a quick comment, I did a little more reading into it and found that ANY connection into RDP will first authenticate successfully as anonymous, and then challenge for login info, so even though those connections say "success" they wouldn't necessarily be successfully authenticating, especially if you have RDP running on that machine for remote administration. Just something to think about, and also to test after changing the registry to make sure that rdp still works. Don't make that change remotely! –  William Harris Nov 30 '13 at 15:55
    
I agree. As in NTLM in example the connection handshake is done, and after the username and password hash are sent. –  yagmoth555 Dec 3 at 2:11

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