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Happy Hacker Digest March 6, 1997
                  ***> Special Internet Explorer Bug Issue <***
         This is a moderated list for discussions of *legal* hacking.
                           Moderator is Carolyn Meinel.
                 OR to the Hackers forum: http://www.infowar.com

                   Please don't send us anything you wouldn't
                  email to your friendly neighborhood narc, OK?

     To subscribe or unsubscribe, just
     use the subscribe boxes on the menubars. If you decide you
      just want to use the forum and not get these mailings, I promise my
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                                 Happy hacking!
"Truth is often eclipsed but never extinguished." -- Livy
URL 'O the Day: http://www.vcalpha.com/silicon/void-f.html This is Silicon
                Toad's current site. It has the best newbie hacker info around.

Table of Contents
   o What is the Internet Explorer Bug?
   o How Do We Fix It?
   o How Do We Exploit It?
   o Security Comparision .URL vs .LNK

*** The MSIE Bug

From the Keys of Carolyn Meinel:

   Thanks to the many people who reported to us the recent discovery
   of a serious bug in Microsoft's Internet Explorer, a program used
   with Windows 95 or Windows NT to browsw the World Wide Web. Special
   thanks to ruben d. canlas jr., who both provided valuable
   information for this issue, and who is also experiemnting with
   moderating the Digest.

   In this special Digest we will give you the details on what the bug
   is, how to exploit it harmlessly, and how to fix it.

*** What is the Internet Explorer Bug?

   First, what is the bug? Bascially, it allows the operator of a bad
   guy Web site to to use ".LNK" and ".URL" files to run programs on a
   remote computer with the Windows 95 or Windows NT operating
   systems. For example, think about visiting a Web site, and having
   it execute the command "format c:" on your computer? Or how about a
   virus? For more details, read the following posts.

From: "Joshua M. Duhl" <Joshua_Duhl@compuserve.com>

   The following story appeared on CNET

   Windows can be hacked through IE
       By Nick Wingfield
       March 3, 1997, 5:15 p.m. PT

       Internet Explorer contains a security hole that could allow
       hackers to completely bypass the browser's built-in checks for
       screening dangerous code.

       The hole, discovered by a trio of students from the Worcester
       Polytechnic Institute last week, is not related to ActiveX, a
       technology for running software components within Explorer that
       has been criticized for being insecure. Instead of creating a
       malicious ActiveX control, the students were able to remotely
       create and delete folders using Shortcuts, a Windows 95 and NT
       feature for triggering actions and applications on the
       operating systems.

       Microsoft today acknowledged that the security hole could allow
       a malicious Web site to delete files and folders from users'
       systems.  However, the students who discovered the glitch
       maintain that it goes beyond those actions, for it could also
       reformat users' hard drives or upload files from their PCs.

       The company is working on a fix for the problem that it hopes
       to post later this evening, according to Dave Fester, lead
       product manager for Internet Explorer. The glitch does not
       affect Netscape Communications' Navigator, according to Geoff
       Elliott, one of the students who found the hole.

       Microsoft has vigorously defended the security protections in
       Explorer, but it appears to have been caught off guard by the
       latest breach.  Explorer contains a feature called Authenticode
       that examines ActiveX controls and Java applets to make sure
       that they have been digitally signed by a trusted source. If
       users ignore the Authenticode warnings about unsigned programs,
       their systems are wide open to attacks.

       A group of German hackers, the Chaos Computer Club,
       demonstrated an ActiveX control in January that made
       unauthorized bank funds transfers from a user's bank account.

       "For executables, we have great security," said Fester. "This
       is going around that. You download a link, and it points you to
       a program on your own computer."

       Instead of executable code, the latest glitch involves ".url"
       and ".lnk" files--also known as Windows 95 and NT Shortcuts. A
       malicious Web site operator could post a link to an ".url" file
       that, for example, creates a folder on a user's computer and
       then deletes it. The Shortcut is able to do that simply by
       remotely activating a command in Windows 95 rather than sending
       code over the network.

       The Worcester students have set up a Web site that demonstrates
       some of the ways in which the hole can be exploited.

       Microsoft's Fester said that a Web site would need to know the
       name of a folder, such as "MSOffice" for Microsoft's Office
       applications, in order to delete it. He also said that none of
       the files or applications in the folder could be deleted if
       they were open. But the Worcester students added today that a
       site could go further than deleting folders and files with a
       Shortcut, possibly even wiping a PC hard disk clean or
       snatching files off a computer.

       One of the Worcester students, Brian Morin, said that the
       security stemmed from Explorer's close integration with

       "It is interesting to note that everybody is so paranoid about
       Java and ActiveX [while] nobody bothered to look at the simple
       and obvious security holes that arise when Internet Explorer is
       tied so closely to the desktop," he said.

       Some analysts echoed that observation. "I suspect more of these
       things will start to appear as Microsoft integrates Explorer
       with Windows," said Ira Machefsky, a senior industry analyst at
       the Giga Information Group.

   Other articles there:
      Actively defending ActiveX
      Intuit warns against ActiveX
      ActiveX used as hacking tool
      CNET Special Report: Crime on the Net
      Battening down the Net's hatches
      Browser bugs hard to catch in Net rush

*** How Do We Fix It?

   Now since we assume that all you folks reading this list are good
   guys, we assume your most important goal is to learn how to fix
   Internet Explorer.  You can get a fix for this bug at


*** How Do We Exploit It?

   You can go to jail warning: You can probably think of many ways to
   make ithis bug become destructive. Since so many people have
   emailed the Supreme Moderator complaining that they don't like to
   be warned of anything illegal, you guys had better skip the rest of
   this message before you get conniptions of the heart.

   This bug allows you to run programs on other people's computers. If
   you want to do this hack, be sure to get permission from the people
   on whose computers you try out this bug. Even though the following
   example is harmless, if the owner of the computer you try it on
   doesn't like you little experiment, you could get in trouble with
   the law.

   Want to go to a Web site where a harmless example of this Internet
   Explorer bug will be run against your Windows computer? See
   Following is some information excerpted from that site.

   It was tested on Microsoft Internet Explorer Version 3.0
   (4.70.1155) running Windows 95. This demo assumes that Windows is
   installed in "C:\WINDOWS". Windows 95 DOES NOT PROMPT BEFORE

   .URL files are WORSE than .LNK files because .URLs work in both
   Windows 95 and Windows NT 4.0 (.LNK's only work in Windows 95).
   .URL files present a possibly greater danger because they can be
   easily created by server side scripts to meet the specific settings
   of a user's system. We will provide .URL files for execution in the
   next day or so.

   The "shortcuts" can be set to be minimized during execution which
   means that users may not even be aware that a program has been
   started. Microsoft's implementation of shortcuts becomes a serious
   concern if a webpage can tell Internet Explorer to refresh to an
   executable. Or worse, client side scripts (Java, JavaScript, or
   VBScript) can use the Explorer object to transfer a BATCH file to
   the target machine and then META REFRESH to that BATCH file to
   execute the rogue command in that file.

*** Security Comparision .URL vs .LNK

   Naturally, the files must exist on the remote machine to be
   properly executed. But, Windows 95 comes with a variety of
   potentially damaging programs which can easily be executed. The
   following link will start the standard calculator which comes with
   Windows 95.

   Windows Calculator (.lnk).
   Windows Calculator (.url).

   This bug can be used to wreak havoc on a remote user's machine. The
   following links will create and delete some directories on a
   Windows 95 machine.

   Create a directory "C:\HAHAHA".
   Open "C:\HAHAHA"
   Remove the directory "C:\HAHAHA"

   The META REFRESH tag can be used to execute multiple commands in
   sequence. This demo copies a .BAT file into your Internet Explorer
   cache and then runs the .BAT file. This .BAT will create a new key
   in your registry called "HKEY_CURRENT_USER/Software/Cybersnot". It
   will then open your AUTOEXEC.BAT and CONFIG.SYS in notepad.
   Finally, it will open REGEDIT so that you can view the key it
   creates. This demo does not destroy anything and should not cause
   any problems on your system. HOWEVER by clicking below, you are
   doing so at your own risk and agree not to hold us liable for any
   problems which may (but probably won't) arise.

Sender: bbuster@succeed.net

   I know you are on BugTraqs to so you know about that IE bug. If i
   were you, I'd NOT mention it on the HH list. That's trouble just
   waiting to explode.  All these newbies that want to hack, but can't
   figure out an e-mail bomber, I bet can sure do html.

   Imagine a site causing a launching a minimised FTP and downloading
   a virus without you knowing it. Then the site getting refreshed
   automaticly and running it. I tryed this right after I got that
   post and it sure as hell works. Another bug I found is be doing a
   <img src="file|/c://whatever"> (this is NOT the "click here" to see
   your hard drive one). This will display a file from ANY local
   drive, or logged into network drive that is refrenced correctly in
   the HTML, on the screen, and with a simple <form type=hidden
   action=email> type of tag, have that displayed file e-mailed to
   whoever you want. This could be real dangerous on an NT system, on
   a network with a direction connection to the net, if you map to
   some important or critical files and the Admin user views the HTML.

   Man-o-man this could be a real Lamer fest. Until these are old news
   I'm not even going to put it on my site.



   Bronc, I appreciate your concern. But I've waited awhile, and gory
   details f how to exploit this bug are being splashed all over the
   place. So I'm going to do what I admire about Silicon Toad's site:
   I'll let people know the problem exists, show them how to get the
   info to exploit it, but exert some degree of social pressure to not
   abuse this knowledge.

   The difference between the Internet Explorer bug and email bombing
   programs is that there is a simple fix that will solve the Internet
   Explorer bug. But in the case of email bombing, the fixes are
   partial and all have serious disadvantages. There are those in the
   computer security industry -- for example Winn Schwartau (and
   myself)-- who regard email bombing as the single most pressing
   problem for the Internet today. I'm afraid email bombing will
   continue to be a growing lamer fest (as you so succinctly put it)
   until we work a better technical solution. But the Internet
   Explorer bug will soon be history.

Carolyn Meinel
M/B Research -- The Technology Brokers
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     Peter Beckman  .  beckman@purplecow.com  .  http://www.purplecow.com/

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