add a local admin user without a pop-up ?

From: me (deros68@yahoo.com)
Date: Fri Dec 01 2006 - 18:44:09 EST


We are conducting a pen test that allows social
engineering emails sent out that may allow us to take
over the the user who opens one of them. I created an
email hack but am now wondering how to add a local
admin user WITHOUT HAVING A DOS PROMPT POP UP WHEN THE
EMAIL IS OPENED.

I cannot transport any files (of any sort - no wscript
file or vbs or any file!!) to the victim and I am
limited to the native XP commands and processes that
are on the victim machine. If I catch a victim (catch
& release) I will be able to reach the victim machine
with native XP means (net use - nc to ports etc..).
The victim then gets scolded about opening
inappropriate emails...

The victim is almost always an administrator or power
user so almost any command or process can be used. I
tried many/many variants of invoking the "Cmd.exe"
shell but so far it always creates a momentary DOS
screen pop-up.

tired many variants similar to below:

CMD.EXE /Q /C net user testx password /add
or
start /B /wait cmd /Q /C c:\windows\system32\net.exe
user testx password /add

pop-ups in either case

I have used rundll32.exe in the past to avoid pop-ups
(in most cases) so I tried:

rundll32.exe netapi32.dll,NetUserAdd
(%COMPUTERNAME%,1,(NEWUSER,PASSWORD),0) (wrapped)

I tried many variants of the above but I always get a
pop up "An Exception occurred while trying to run
netapi32.dll.."

OK

I plugged netapi32.dll into Olly and saw the dll entry
NetUserAdd takes 4 parms -but the 3rd parm
is a LBYTE pointer to the input buffer. I wonder if
rundll32.exe can construct such a pointer for me?

Using only the programs and API calls available from
what is essentially an XP DOS shell - does anyone have
a better way to do this without creating a DOS pop-up
?

I have already figured out how to write the "net user
Username PSWD /add" & "net localgroup administrators
Username /add" cmds to the registry (the run key) -
without creating a pop-up! (Silently..)

However, the problem with the above is that it
requires a logon/logoff or re-boot to occur before the
user is added. Thus my quest for a silent (no pop-up)
but immediate means to do this.

Since the email interface can call a winapi - I may
have to try to call netapi32.dll/NetUserAdd - I hope
that I do not have to do that - the test may be over -
before I can decipher the correct syntax between my
email system and the STDCALL Winapi

Thanks

 
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