Internet Explorer Bug #4

[pokee () MAXWELL EE WASHINGTON EDU (Aaron Spangler)]

Included below is IE Bug#4 I would like to post.
It can be found at:

http://www.ee.washington.edu/computing/iebug/


Internet Explorer Exploit #4

The exploit works for both Netscape Navigator 3.01 and Microsoft Internet
Explorer 3.01 with Security Patches. (earlier versions should work as
well, but have not yet been tested).
Look below to see how it works.


****How it Works******

Web page that points to a Rogue SMB Server

This web pages contains an embedded image (actually two).  The embedded
images do not reside in this same directory as this web page.  In fact,
they reside on a SMB Lanman server (as opposed to an HTTP server).  (View
the source for this html to get a better idea what I am talking about).
I borrowed this idea from the
<A href=http://dec.dorm.umd.edu/>Last MS Internet Explorer Security Exploit.</A>

The modified SMB Server

In order for the client to download the images, the client needs to
'logon' to the Lanman server.  Windows NT seems to do this without even
asking the user for confirmation.  Windows NT simply forwards the username
and encrypted version of the user's password to the Lanman server. The
Lanman server code has been modified slightly to record Usernames and
"Hashed Passwords" of the victims.  Also the code has been modified to
supply the client with a <b>fixed</b> "Challenge seed value" for password
encryption.  (Thus making it even easier to decode the client passwords
in the future.)
See <a href=nt_pw_dict_attack.txt>NT
Password Dictionary Attack</a> for where I got the Lanman server idea.

What's the big deal?

First of all, no remote web site should be able to record your username.
If they do, then can compile junk email lists and sell your name.
Secondly, if they have information on what your password might be, and
they know what site you came from, they can gain access to your computer
or local account.  (Thus compromising your security with you never knowing
about it.) It is fairly easy to unencrypt a MS password if the challenge
has set to zero via dictionary attacks.  Sequential search brute force
attacks work as well if you can guess what types of characters are most
common in the password.  Yes, it is time consuming, but if your account
gets hacked, is it really worth it?

It is interesting to note that in theory someone could setup a Lanman server
that make a simultaneous connection back to the client as a connection
comes in.  By simply relaying the same challenge and password back to the
client, the remote server could gain network access to the vulnerable client.

<h4> Did you really get my username & hashed password? </h4>
Take a look at the <a href=passout.txt>log so far.</a> Remember these passwords are easier to unencrypt because the 
challenge response is set to all zeros!

<hr>
<address>
IE BUG #4, by <a href=/staff/spangler.html>Aaron Spangler</a>
</address>

--
Aaron Spangler                 EE Unix System Administrator
Electrical Engineering FT-10        pokee () ee washington edu
University of Washington            Phone    (206) 543-8984
Box 352500                             or    (206) 543-2523
Seattle, WA 98195-2500              Fax      (206) 543-3842