RE: security-basics Digest 18 Jun 2003 22:09:15 -0000 Issue 618

[<dave () netmedic net>]

Unlike many Telnet services, the Microsoft Telnet Server service offers a
method of secure logon using NTLM security. Most services allow for only a
"clear text" logon, which sends your password across the network in an
unencrypted form.

Telntadmn.exe allows the following security settings.

AllowTrustedDomain
AltKeyMapping
DefaultDomain
DefaultShell
MaxFailedLogins
NTLM
TermCap
NumThreadsPerProcessor



You can turn NTLM on with it, or edit the registry:

HKEY_LOCAL_MACHINE\Software\Microsoft\TelnetServer\1.0 
NTLM   REG_DWORD  
0x00: Disables Windows NT LAN Manager (NTLM) authentication.
0x01: Attempts NTLM first, and then uses clear text
authentication.
0x02: Uses NTLM authentication only.

Now you can force the W2000 server to use NTLMv2 only with the
lmcompatibilitylevel REG_DWORD set to 5.  I do not know how that will effect
the telnet server but at least you can have NTLM.  But the DefaultDomain
edit in the TelnetServer key forces it to use the default domain for
authentication. I will try to see if forcing to NTLMv2 causes the telnet to
use NTLMv2 or does it still only use NTLM.

I would suggest all these registry edits as well.

machine\system\currentcontrolset\control\lsa\secureboot=4,1
machine\system\currentcontrolset\control\lsa\fullprivilegeauditing=3,1
machine\system\currentcontrolset\control\lsa\lmcompatibilitylevel=4,5
machine\system\currentcontrolset\control\lsa\restrictanonymous=4,2
MACHINE\System\CurrentControlSet\Control\Lsa\SubmitControl=4,0
MACHINE\System\CurrentControlSet\Control\Lsa\NoLMHash\bar=4,0

http://support.microsoft.com/default.aspx?scid=kb;EN-US;225233



http://support.microsoft.com/default.aspx?scid=kb;EN-US;226107


http://support.microsoft.com/default.aspx?scid=kb;en-us;201194




 
_____________________
Dave Kleiman
dave () netmedic net
www.netmedic.net

"High achievement always takes place in the framework of high expectation."
Jack Kinder

 

-----Original Message-----
From: Damon McMahon [mailto:inst_karma () hotmail com] 
Sent: Wednesday, June 18, 2003 22:45
To: deppdm () ornl gov
Cc: security-basics () securityfocus com
Subject: Re: security-basics Digest 18 Jun 2003 22:09:15 -0000 Issue 618

Dennis,

Running windump on a Windows 2000 client and tcpdump on a MacOSX 10.1 client

shows the login: and password: transmitted in clear text to a Windows XP 
telnet server.

Can you specify any documentation stating NTLM is used?

Thanks in advance,
Damon


> The telnet built into Windows 2000 uses NTLMv2 authentication by defalt.  
> While
> this is not 3DES or RC4, it is still not plain text.
>
> Dennis

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