Discussion in 'malware problems & news' started by sergey ulasen, Jul 12, 2010.

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  1. Sadeghi85

    Sadeghi85 Registered Member

    rundll32.exe only gets involved when you double click the shortcut, what do you do about explorer.exe? ;)

  2. CloneRanger

    CloneRanger Registered Member


    Just recently seen the newer replies in that thread, and will be responding ;)
  3. CloneRanger

    CloneRanger Registered Member

    The .lnk POC provided by - - ONLY works if you copy dll.dll into c:\ first.

    As Rmus has said

    I must admit i overlooked that aspect when testing, and so did a lot of other people :(

    Yes it goes to prove how .lnk works so :thumb: but how would ANY associated nasty get into c:\ etc without a system/app being set up to allow the transfer ?

    Maybe i'm missing something, if so please elaborate ;)


    I deleted dll.dll from C:\ and tried the POC again from both my USB stick and a folder on my desktop. This time just cruising and double clicking showed NO entry in DbgView ! = Fail
    Last edited: Jul 24, 2010
  4. Rmus

    Rmus Exploit Analyst

    Yes, it is a reactive solution, rather than a proactive one.

    A better solution is to White List the executables on the system. Then, you don't care what rundll32.exe does as long as it doesn't attempt to load a non-white listed DLL.

    This is easy to test White Listing security.

    Here, I use rundll32.exe in an autorun.inf file to load the hmmapi.dll which starts IE with Windows Hotmail:

    shellexecute=rundll32.exe hmmapi.dll,MailToProtocolHandler %1


    Rundll32.exe can happily do its task since the hmmapi.dll is an authorized executable.

    Now, I use a different version of the hmmapi.dll - not white listed on my system - and rundll32.exe is not permitted to load the DLL:


    The problems with setting rundll32.exe to prompt are

    1) where do you stop in trying to figure out how an exploit is going to use a system file? You can end up prompting many Windows systems files and effectively cripple the system.

    2) you get many false positives. Check the ProcessGuard archives here at Wilders and search for rundll32.exe. You will find many unhappy PG users who complained about this very thing: how to you deal with these system executables?

    Last edited: Jul 24, 2010
  5. Rmus

    Rmus Exploit Analyst

    Yes, the exact exploit in the wild had everything on USB stick. This exploit cannot be tested unless you get the USB stick itself, since the .lnk files are hardcoded to point to a specific device.

    A better test is to put a non-white listed executable on a USB device and create a shortcut to that executable. Now, the .lnk file will not execute automatically, but you can simulate the exploit by manually clicking on the .lnk file.

    The same result occurs: the executable file is launched.

    Or, maybe not, if you have proper protection in place.

    Here, I use an old leaktest file, firehole.exe, not white listed on my system. I create a shortcut to it and attempt to run it. It goes nowhere. End of exploit.


    Last edited: Jul 24, 2010
  6. i_g

    i_g Registered Member

    The real exploit doesn't execute an executable, it loads a DLL - which might be pretty different (protection-wise).
  7. Rmus

    Rmus Exploit Analyst

    Yes, they are spoofed with the .tmp file extension:

    W32.Stuxnet Installation Details
    I showed in Post #179 blocking the loading of a DLL. Without having the complete exploit on a USB device, people can only simulate the attack.

    Any attempt to access those files flags an alert here:


  8. Meriadoc

    Meriadoc Registered Member

    Very nice post by Peter Silberman on M-unition the MANDIANT blog, I hadn't read it until the link was posted here so:thumb:
  9. CloneRanger

    CloneRanger Registered Member

    Some more info etc



    Glad you liked it :)
  10. MrBrian

    MrBrian Registered Member

  11. Sadeghi85

    Sadeghi85 Registered Member

  12. Sadeghi85

    Sadeghi85 Registered Member

    W32.Stuxnet – Network Operations

    SUPERIOR Registered Member

    guys, i have some noobish questions, hope no one bothered by answering them
    anyone tried comodo aganist this rootkit? i mean D+ aganist shortcut vul?
    if i can get a sample of this rootkit? is it safe to run it in shadow mode?
    i read Mandiant blog about this malware, it's using // instead of / in directory for process, is this called "hook" or "inject"?
    @Ramus ....whats this environment you were using to test the malware if you dont mind my question?
    Thanks in advance
  14. Ford Prefect

    Ford Prefect Registered Member

  15. AvinashR

    AvinashR Registered Member

  16. CloneRanger

    CloneRanger Registered Member


    Thanks for the SophosLabs Free Tool link :thumb:

    More info and videos from the direct link AvinashR gave :thumb:

    Installed it and it worked to stop the POC from both my USB stick and desktop, as viewed in DbgView. But i didn't get an alert box as seen in the video ?

    @Ford Prefect

    Nice find :thumb:

    G Data LNK-Check

    Anyway kudos to Sophos and G Data for releasing these, they should help a lot of people till a permanent fix arrives, if the word is spread about them, and used correctly ;) The Sophos one does appear less risky though.

    Wonder if these tools are using the LinkIconShim trick in some way in Post 184 ?


    Thanks, W32.Stuxnet Network Information already in Post #175 ;)
  17. AvinashR

    AvinashR Registered Member

    As per LinkIconShim :-

    The Sophos Windows Shortcut Exploit Protection Tool doesn't handle all malicious link files due to mishandling of the .lnk internal data..

    Now how can we test this thing?

  18. AvinashR

    AvinashR Registered Member

  19. Kid Shamrock

    Kid Shamrock Registered Member

  20. AvinashR

    AvinashR Registered Member

  21. Sadeghi85

    Sadeghi85 Registered Member

    This one is Network Operations. ;)

    + that Sophos tool doesn't seem to work if the dll/lnk files are on the hard drive.

  22. EraserHW

    EraserHW Malware Expert

    This behavior was expected. Due to the nature of the flaw (design flaw) it is pretty difficult to develop a fully working patch. You can't exactly understand which LNK is malicious and which one is not. While waiting for Microsoft patch, solutions are two:

    1) heuristically try to detect the malicious file (i.e. the linked file is loaded from removable device and/or network), but this will leave some vulnerability if the LNK is located on hard drive;

    2) totally filtering the vulnerable function, this will prevent every LNK from exploiting it, but this filter will cut off some legitimate LNK icons too (it is still far better than having all LNK shortcuts with blank icon)

    I've developed my own patch SafeLink and choosed the 2nd way currently ;) I've uploaded a sample video on Youtube
  23. AvinashR

    AvinashR Registered Member

    Please share this technique with us... :)
  24. CloneRanger

    CloneRanger Registered Member

    Well spotted sorry, thanks ;)

    I've seen reports of both the Sophos a Gdata tools failing :(


  25. CloneRanger

    CloneRanger Registered Member

    You might be surprised how many people will actually do that :eek:
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