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Re: Problem with account-lockouts if local-accounts are defined in a dom

Subject: Re: Problem with account-lockouts if local-accounts are defined in a domain.
Date: Tue, 04 Apr 2006 10:21:17 -0400
You should update your plugins.
I changed smb_login.nasl some times ago to first try to connect with the
given domain name instead to first try to connect with no domain name.


Nicolas


On Tue, 2006-04-04 at 09:10 +0200, m g wrote:
After further investigating this issue, it appears that the 
SMB/domain-entry is not set at all during the scans I performed, so the 
previous conclusion I made is incorrect. It turns out that the plugin 
smb_login_as_users.nasl tries to login to the specified host with the 
enumerated username and a combination of a blank password and a password 
same as the username, however a domainname is not provided. The 
Windows-host first tries to login locally with the supplied credentials 
and it turn out that the windows-host (not Nessus) then tries to login 
to the domain with the supplied credentials (note again that no 
domain-name was supplied to the logon-function).

I also manually verified this (not using Nessus) by connecting to a 
share (net use \\servername\share "invalid_password" /user:"username) of 
the Windows-host supplying only a username and invalid password. It 
turns out that two logons are performed, one locally with the supplied 
credentials and one in the domain.

Now the key question: Is this a problem in the Nessus-plugin (which 
should supply a valid hostname/domain to login to) or is this a problem 
with Windows in how it handles logon-requests that lack the domainname. 
Also is it perhaps possible to tune Nessus so that it always supplies 
the proper domain/hostname.

Of course, the obvious solution, enabling safe-checks etc. results in 
the plugin not being performed, however this is not an option in my 
situation.

Thanx again if anyone can provide me a solution.

Mike

m g wrote:
Hello,

Consider the following scenario:
Several workstations or servers that are domain-members contain a 
local useraccount (ie. testuser). In the domain also an account named 
testuser is defined.

In the above configuration I've experienced the following problem. 
While scanning some systems that are members of the domain, nessus 
tries to login to the local system using several combinations 
(username / no password, username / password=username). This results 
in two logons per enumerated account. However the scan also tries to 
login on the domain using the locally enumerated account. This means 
that for the testuser-account, scanning four domain-members results in 
eight invalid logins ==> result is that the domain-account is locked.

As far as I could see, the problem is related to the 
smb_login_as_users.nasl. This plugin tries to login using the locally 
enumerated accounts and uses the SMB/domain entry from the knowledge 
base. I did not define the SMB-domain in my nessusrc-file, however 
further investigation turns out that other plugins set the 
SMB/domain-entry, for example if NULL-sessions are enabled (true for 
my configuration), the smb_login.nasl sets the SMB/domain entry. 
According to my opinion, because of NULL-sessions being enabled, the 
smb_login_as_users.nasl now tries to authenticate local users against 
the domain.

Anyone else experienced this problem and if so, any advice on how this 
can be solved.

Thanx in advance.

Mike

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