Printer Friendly Page

Discovered: November 27, 2003
Updated: February 13, 2007 12:14:23 PM
Type: Worm
Systems Affected: Windows

W32.Midlak@mm is a mass-mailing worm that spreads through email, IRC, and the Kazaa file-sharing network. It deletes system files and steals information about the computer on which it runs. It is packed with UPX.

Antivirus Protection Dates

  • Initial Rapid Release version December 01, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version December 01, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date December 03, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Fergal Ladley

Discovered: November 27, 2003
Updated: February 13, 2007 12:14:23 PM
Type: Worm
Systems Affected: Windows

When W32.Midlak@mm is executed, it performs the following actions:

  1. Copies itself into the root of the current drive as Angeline_jolie.scr.

  2. Copies itself to the \Program Files\KaZaA\My Shared Files folder, if it exists, using the following file names:
    • MSN Crack (works).exe
    • Ana_Kurnikova_XXX.scr
    • CreditCard Gen2003.exe
    • ICQ DDoS.exe
    • Office 2003 KeyGen .exe
    • PayPal.com hack.exe
    • WinXP KeyGen.exe
    • XXX Search Engine2003.exe
    • YahooMail hack .exe

  3. Attempts to create the following files:
    • \mIRC\Script.ini, which overwrites the existing Script.ini, if present
    • %System%\Ossmtp.dll, a legitimate .dll file containing SMTP functionality
    • \Setuplogs.vbs, a Visual Basic script that searches all drives for email addresses
    • %System%\emls.tmp, a text file created by Setuplogs.vbs
    • C:\ReAd_ThiS_S**T_NoW.txt, a text file

      Note: %System% is a variable. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  4. Adds the value:


    to the registry key:


    so that W32.Midlak@mm runs when you start Windows.

    • %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.
    • Due to bugs in the code, the file %Windir%\Wupdm32.exe is not created, and therefore the worm will not run when Windows is started.

  5. Searches for the files with the following extensions:
    • .asp
    • .htm
    • .html
    • .txt

      on all the drives, and then saves any email addresses found in those files to the file, %System%\emls.tmp.

  6. Sends a message to a predetermined email address to report the infection. The worm uses a legitimate .dll, Ossmtp.dll, to send email messages via SMTP. The name of the used SMTP server is retrieved from the following registry key:

    HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Server

  7. The email contains the following registry values:
    • HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Server
    • HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Email Address
    • HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Display Name
    • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\

  8. Sends itself to the email addresses in %System%\emls.tmp. The sender's address is retrieved from the following registry key:

    HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Email Address

  9. The email will have one of the following subject lines, followed by a space and a random, four-digit number:
    • Upozorenje
    • Zbog cega spamujete
    • Zadnja opomena!
    • Postovanje! Molim Vas Procitajte!
    • Ovo nema smisla!
    • Re: Order!
    • Order from ScreenSeaver.com
    • Re: ScreenSeaver Order
    • Re: ScreenSaver...
    • Your order - ScreenSeaver!
    • Warning!!!
    • Why you spam us ?
    • Last notice!
    • Regard ! Please read...
    • This is not OK !

  10. The email will have an attachment, which is the executable file of the worm. There are two possible types of file names.
    • The first type is composed of four parts, as follows:

      1. The first part of the name is one of the following strings:
        • XXX_
        • Sexy_
        • Only_
        • Jeah_
        • Hmmm_

      2. The second part of the name is one of the following strings:
        • Ana_Nikolic
        • Jelena_Karleusa
        • Carmen_Electra
        • Jennifer_Lopez
        • Natasa_Bekvalac
        • Ana_Kurnikova
        • Olja_Karleusa
        • Angeline_Jolie
        • Sylvia_Saint
        • Vesna_Pisarovic

      3. The third part of the name is a string of four random digits. This will be the same string that appears in the subject line.

      4. The fourth part of the name will be one of the following extensions:
        • .scr
        • .exe

          For example, the name could be either of the following:
          • XXX_Sylvia_Saint8647.scr
          • Only_Vesna_Pisarovic9843.scr

    • The second type is also composed of four parts, as follows:
      1. The first part of the name is one of the following strings:
        • log
        • logs
        • file
        • mail
        • smtp

      2. The second part of the name is two instances of the string of random digits as appeared in the subject line. (Such as 52055205.)

      3. The third part of the name is a space, followed by a hyphen, then another space.

      4. The fourth part of the name is one of the following strings:
        • www.telekom.scr
        • www.eunet.scr
        • www.yugodata.scr
        • www.neobee.scr
        • www.drenik.scr
        • www.ptt.scr
        • www.memodata.scr
        • www.arkayunet.scr
        • www.nic.yu.scr
        • www.treointer.scr

          For example, the name could be either of the following:
          • file52055205 - www.drenik.scr
          • smtp43984398 - www.ptt.scr

  11. The body of the email will be similar to one of the following three messages:
    • Body #1:
      Dear Customer,

      Thank you for ordering our screensaver...

      1. <name of attachment> (top rated) -   $7.95

      Subtotal: $7.95
      Shipping & Handling: $0.00
      Tax: $0.00
      Total: $7.95
      We have sent you the requested screensaver!
      Your Screensaver was sent with this e-mail, and you can find it in the attachment ><name of attachment><
      If you have any questions about this order or the products/services you've purchased, please feel free to:
      Contact our Customer Orientation Group at 480-505-8888
      Email us at support@screenseaver.com
      Thank you for ordering our screensaver...
      <value of HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Display Name>

    • Body #2:
      Dear Sir,
      According to our cognitions you have done next:
      actually you have been buring our network and our right is to protect our users.
      Accourding to that you have been informed about this by phone by our System engineer,
      with this letter we want to point you to next facts:
      1) Your personal account is not restricted in any way and our right is to protect our users and servers;
      2) Server mail.0web-0hosting.com has been shuted down beacouse large amount of emails that have been
      arricing to our servers and beacouse of adequacy suspicion that it is a spam ramp.
      3) Unsubscribing system is not functioning!
      On unsubscribing attempt result is next:
      Persits.MailSender.4 error '800a0004'
      Connection timed out.
      The emails are still arriving...
      According to part 10 of Personal servie terms of use we are authorized to warn you about this.
      As an evidence we have a LOG file fromour server that is clearly showing date and time when you
      have been sending spam emails, your IP address and your username!
      Please accept this warnning about sending informations to users and wrongly interpret our actions taken in your case as seriously as possible.
      If you don't accept this warning we will be forced to refer to our lawyers so we could protect our company intersts.
      If you don't understand anything in this email, please contact us via email or by phone for aditional explanations.
      According to computer criminal law of USA, act 168v, act you have done is judget to
      jail (1-8 years).
      Best regards,
      <value of HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Display Name>,
      Office Manager

    • Body #3:
      Postovani,Vi ste prema nasem saznanju cinili sledece:
      Spam-ovanje Servera Provajdera putem slanja istovetnih poruka na veliki
      broj adresa na Internetu i time prakticno nasu mrezu zasipali velikim
      kolicinama mail-ova i nase je pravo da zastitimo korisnike.
      S obzirom da ste obavesteni putem telefona od strane System inzinjera o
      svemu,ovim putem i pismeno zelimo da vam ukazemo na sledece :
      1. Vas nalog personal nalog nichim nije ogranichen, nase pravo je da
      maskimalno zastitimo nasu mrezu i servere od  spama.
      2. Server mail.0web-0hosting.com je iskljucen pre dve nedelje zbog
      velike kolichine maila koja je stizala na nashe servere, ali i zbog
      osnovane sumnje da je taj server spamerska rampa.
      3. Ne funkcionishe sistem za skidanje s liste!

      Pokusaj  unsubscribovanja, rezultat je sledeci:
      Persits.MailSender.4 error '800a0004'
      Connection timed out.
      mailovi su nastavili da dolaze...
      U skladu s clanom 10. Opstih uslova koriscenja Personal servisa mi smo
      ovlasceni da u navedenom slucaju Vas opomenemo.
      U prilog nashoj tvrdnji,je LOG fajl sa naseg servera sa kojeg se vidi
      vasa IP adresa , kao i Vas username!
      LOG fajl sa naseg servera je pre 3 dana i tacno se vidi vreme i datum
      kada ste slali mailove!
      Zamolicu Vas da krajnje ozbiljno shvatite nase upozorenje u vezi slanja
      informacija korisnicima, cime pogresno interpretirate nase postupke u
      odnosu na vas.
      Ukoliko se oglusite na nase upozorenje  bicemo prinudjeni da se
      obratimo advokatima  kako bi na taj nacin zastitili interese nase kompanije.
      U slucaju da imate bilo kakve nedoumice u vezi s ovim dopisom, molimo
      Vas da nam posaljete e-mail ili se javite na nas telefon radi dodatnih
      Prema zakonu Srbije i Crne Gore o kompljuterskom kriminalu po clanu
      186v za ovo delo koje ste ucinili predvinjena je kazna zatvorom od jedne
      do osam godina.

      S postovanjem,
      <value of HKEY_CURRENT_USER\Software\Microsoft\InternetAccount Manager\Accounts\00000001\SMTP Display Name>
      Office Manager

  12. On the 13th day of the month, attempts to delete files with the following extensions:
    • .exe
    • .sys
    • .ini

      from the %System% and %Windir% directories.

  13. Displays the following message box:


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Fergal Ladley

Discovered: November 27, 2003
Updated: February 13, 2007 12:14:23 PM
Type: Worm
Systems Affected: Windows

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan and delete all the files detected as W32.Midlak@mm.
  4. Delete the value that was added to the registry.
For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder ," Article ID: Q263455.

2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Scanning for and deleting the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.Midlak@mm, click Delete.

4. Deleting the value from the registry

WARNING: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to the key:


  4. In the right pane, delete the value:


  5. Exit the Registry Editor.

Writeup By: Fergal Ladley