Discovered: June 17, 2002
Updated: February 13, 2007 11:49:17 AM
Also Known As: W32.Yaha.D@mm, I-Worm.Lentin.e [AVP], W32/Yaha.e@MM [McAfee], W32/Yaha-D [Sophos], WORM_YAHA.D [Trend], Win32.Yaha.D [CA]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2001-0154


W32.Yaha.E@mm is a mass-mailing worm that sends itself to all email addresses that exist in the Microsoft Windows Address Book, the MSN Messenger List, the Yahoo Pager list, the ICQ list, and files that have extensions that contain the letters ht. The worm randomly chooses the subject and body of the email message. Depending upon the name of the Recycled folder, the worm either copies itself to that folder or to the %Windows% folder.

The name of the file that the worm creates consists of six randomly generated numbers.

NOTE: Virus definitions dated prior to June 18, 2002 will detect this as W32.Yaha.D@mm

Antivirus Protection Dates

  • Initial Rapid Release version June 18, 2002
  • Latest Rapid Release version June 18, 2002
  • Initial Daily Certified version June 18, 2002
  • Latest Daily Certified version June 18, 2002
  • Initial Weekly Certified release date June 19, 2002

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


Technical Description


If W32.Yaha.E@mm runs, it does the following:

It attempts to send itself to all email addresses that exist in the Windows Address Book file, the MSN Messenger List, the Yahoo Pager list, the ICQ list, and files with extensions that contain the letters ht. The email addresses are then stored in the file \%Windows%\<six random numbers><six random numbers>.dll

For example, if the six random numbers are 123456, then the file name will be \%Windows%\123456123456.dll.

NOTE: %Windows% is a variable. The worm locates the \Windows folder (by default this is C:\Windows or C:\Winnt) and copies itself to that location.

The worm masks its activity by displaying the several strings of text, and then causing the Windows desktop to appear to shake. This is done to make it look like a screen saver. The displayed text strings are:

  • U r so cute today #!#!
  • True Love never ends
  • I like U very much!!!
  • U r My Best Friend

Email routine details
URL
When the worm runs its email routine, it chooses the URL that it is supposed to have originated from by merging a string from the following set of strings:

screensaver, screensaver4u, screensaver4u, screensaverforu, freescreensaver, love, lovers, lovescr, loverscreensaver, loversgang, loveshore, love4u, lovers, enjoylove, sharelove, shareit, checkfriends, urfriend, friendscircle, friendship, friends, friendscr, friends, friends4u, friendship4u, friendshipbird, friendshipforu, friendsworld, werfriends, passion, bullsh*tscr, shakeit, shakescr, shakinglove, shakingfriendship, passionup, rishtha, greetings, lovegreetings, friendsgreetings, friendsearch, lovefinder, truefriends, truelovers, or f*cker

with:

.com, .org, or .net

For example, it might name the URL Screensaver.com.

From:
The From field is a randomly-selected email address and may not be the legitimate sender.

Subject
W32.Yaha.E@mm randomly chooses the subject from the following strings:
"Fw: ", " ", ":-)", "!", "!!", "to ur friends", "to ur lovers", "for you", "to see", "to check", "to watch", "to enjoy", "to share", "Screensaver", "Friendship", "Love", "relations", "stuff", "Romantic", "humour", "New", "Wonderfool", "excite", "Cool", "charming", "Idiot", "Nice", "Bullsh*t", "One", "Funny", "Great", "LoveGangs", "Shaking", "powful", "Joke", "Interesting", "U realy Want this", "searching for true Love", "you care ur friend", "Who is ur Best Friend ", "make ur friend happy", "True Love", "Dont wait for long time", "Free Screen saver", "Friendship Screen saver", "Looking for Friendship", "Need a friend?", "Find a good friend", "Best Friends", "I am For u", "Life for enjoyment", "Nothink to worryy", "Ur My Best Friend ", "Say 'I Like You' To ur friend", "Easy Way to revel ur love", "Wowwwwwwwwwww check it", "Send This to everybody u like", "Enjoy Romantic life", "Let's Dance and forget pains", "war Againest Loneliness", "How sweet this Screen saver", "Let's Laugh ", "One Way to Love", "Learn How To Love", "Are you looking for Love", "love speaks from the heart", "Enjoy friendship", "Shake it baby", "Shake ur friends", "One Hackers Love", "Origin of Friendship", "The world of lovers", "The world of Friendship", "Check ur friends Circle", "Friendship", "how are you", "U r the person?", "Hi", or "¯"

Message
The message will be:

<HTML><HEAD></HEAD><BODY>

followed by:

<iframe src=3Dcid:[SomeCID] height=3D0 width=3D0></iframe>

or

[nothing]

This is followed by:

<FONT></FONT>

followed by:

[text that is gathered from .doc and .txt files on the infected computer.]
.
.
Check the attachment too..
<<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>
    or

    Hi Dear
    Check the Attachement ..
    See u
    <Infected Computer's Username>

    ----- Original Message -----
    From: "Friendship" < friendshipscr@[URL constructed above] >
    To: < [Infected User's e-mail Address] >
    Sent: Friday,  May 11, 2002 8:38 PM
    Subject: [Subject constructed above]

    This is followed by:

    This e-mail is never sent unsolicited. If you need to unsubscribe,
    follow the instructions at the bottom of the message.
    ***********************************************************
    Enjoy this friendship Screen Saver and Check ur friends circle...
    Send this screensaver from www.[URL constructed above] to everyone you
    consider a FRIEND, even if it means sending it back to the person
    who sent it to you. If it comes back to you, then you'll know you
    have a circle of friends.
    * To remove yourself from this mailing list, point your browser to:
    http://[URL constructed above]/remove?freescreensaver
    * Enter your email address ([infected user's e-mail address]) in the field provided and click "Unsubscribe".

    or

    * Reply to this message with the word "REMOVE" in the subject line.
    This message was sent to address  [infected user's e-mail address]
    X-PMG-Recipient: [Infected Username]
    <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>
      The message closes with:

      </BODY></HTML>

      Attachment
      The attachment name is constructed from the following file names:
      • loveletter
      • resume
      • biodata
      • dailyreport
      • mountan
      • goldfish
      • weeklyreport
      • report
      • love

      followed by:
      • .doc
      • .mp3
      • .xls
      • .wav
      • .txt
      • .jpg
      • .gif
      • .dat
      • .bmp
      • .htm
      • .mpg
      • .mdb
      • .zip

      with one of the following extensions:
      • .pif
      • .bat
      • .scr

      The worm uses its own SMTP Engine. It attempts to use the infected computer's default SMTP server to send mail. If it cannot find that information, then it uses one of many SMTP server addresses that are hardcoded into the worm.

      Additional functions
      In addition to the mass-mailing routine, the worm does the following:

      It randomly uses the "Incorrect MIME header" exploit, which allows automatic execution of the worm on unpatched systems.

      It will attempt to terminate Anti-Virus and Firewall processes. It enumerates the active processes and if the process name is one of the following it will attempt to terminate the process:
      • SCAM32
      • SIRC32
      • WINK
      • ZONEALARM
      • AVP32
      • LOCKDOWN2000
      • AVP.EXE
      • CFINET32
      • CFINET
      • ICMON
      • SAFEWEB
      • WEBSCANX
      • ANTIVIR
      • MCAFEE
      • NORTON
      • NVC95
      • FP-WIN
      • IOMON98
      • PCCWIN98
      • F-PROT95
      • F-STOPW
      • PVIEW95
      • NAVWNT
      • NAVRUNR
      • NAVLU32
      • NAVAPSVC
      • NISUM
      • SYMPROXYSVC
      • RESCUE32
      • NISSERV
      • ATRACK
      • IAMAPP
      • LUCOMSERVER
      • LUALL
      • NMAIN
      • NAVW32
      • NAVAPW32
      • VSSTAT
      • VSHWIN32
      • AVSYNMGR
      • AVCONSOL
      • WEBTRAP
      • POP3TRAP
      • PCCMAIN
      • PCCIOMON

      Depending upon the name of the Recycled folder, the worm copies itself to either that folder or to the \%Windows folder. The file name consists of six random numbers.

      The worm configures itself to execute each time that an .exe file is executed by changing the default value of the registry key

      HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command

      to

      [WormName]" %1 %*

      It also creates a randomly named text file in the Windows folder; for example, [Random File Name].txt. The file contains the following text:

      <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>
      w32.yAHa.D
      aUThor :H^H,h2h@achayans.com
      oRigIN :inDia,kERala(gODs oWn cOUntrY)
      kANagaaa ,mANdi pEnnee nJan Ninne sNEhikkunnuu..
      oRu sITe kITTiyirunnegggil.. hACk CHEyyyamayirunnuuu..

      <<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>


      Recommendations

      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.


      Removal


      Removal using the removal tool
      Symantec has provided a tool to remove infections of W32.Yaha.E@mm and W32.Yaha.F@mm. Click here to obtain the tool. This is the easiest way to remove these threats and should be tried first.

      Manual removal procedure

      1. If the worm has already run, you must first reverse the change that the worm made to the registry. If the worm has not run, go to step 2.
        1. Configure Windows to show all files.
        2. Copy Regedit.exe to Regedit.com (in most cases).
        3. Edit the registry and reverse the change that the worm made.
      2. Update the virus definitions, run a full system scan, and delete all files that NAV detects as W32.Yaha.E.
      For detailed instructions on how to do this, see the sections that follow.

      To configure Windows to show all files:
      1. Start Windows Explorer.
      2. Click the View menu (Windows 95/98/NT) or the Tools menu (Windows Me/2000/XP), and then click Options or Folder options.
      3. Click the View tab.
      4. Uncheck "Hide file extensions for known file types."
      5. Do one of the following:
        • Windows 95/NT: Click "Show all files."
        • Windows 98: In the Advanced settings box, under the "Hidden files" folder, click Show all files.
        • Windows Me/2000/XP: Uncheck "Hide protected operating system files" and under the "Hidden files" folder, click "Show hidden files and folders."
      6. Click Apply, and then click OK.

      To copy Regedit.exe to Regedit.com:
      Because the worm modified the registry so that you cannot run .exe files, you must first make a copy of the Registry Editor as a file with the .com extension, and then run that file.
      1. Do one of the following, depending on which version of Windows you are running:
        • Windows 95/98: Click Start, point to Programs, and click MS-DOS Prompt.
        • Windows Me: Click Start, point to Programs, point to Accessories, and then click MS-DOS Prompt.
        • Windows NT/2000/XP:
          1. Click Start, and click Run.
          2. Type the following and then press Enter:

            command

            A DOS window opens.
          3. Type the following and then press Enter:

            cd \winnt
          4. Proceed to the next step.
      2. Type the following and then press Enter:

        copy regedit.exe regedit.com
      3. Type the following and then press Enter:

        start regedit.com

        The Registry Editor will open in front of the DOS window. After you finish editing the registry, exit the Registry Editor, and then exit the DOS window, as well.
      1. Proceed to the next section, "To edit the registry and reverse the change that the worm made," only after you have accomplished the previous steps.

      To edit the registry and reverse the change that the worm made:

      CAUTION : Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
      1. Navigate to and select the following key:

        HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command

        CAUTION: The HKEY_LOCAL_MACHINE\Software\Classes key contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with an .exe extension from running. Make sure that you browse all the way along this path until you reach the \command subkey.

        Modify the HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command subkey that is shown in the following figure:

        <<=== NOTE: Modify this key.
      2. In the right pane, double-click the (Default) value.
      3. Delete the current value data, and then type: "%1" %* (That is, type the following characters: quote-percent-one-quote-space-percent-asterisk.)

        NOTE: Registry Editor will automatically enclose the value in quotation marks. When you click OK, the (Default) value should look exactly like this:
        ""%1" %*"

        Make sure that you completely delete all value data in the command key before you type the correct data. If you leave a space at the beginning of the entry, any attempt to run program files will result in the error message, "Windows cannot find .exe." If this happens to you, start over at the beginning of this document, and make sure that you completely remove the current value data.
      4. Restart the computer.
      5. If you have not already done so, run Live Update, and then run a full system scan as described in the following section, "To scan with Norton AntiVirus and delete the infected files."

      To scan with Norton AntiVirus and delete the infected files:
      1. Obtain the most recent virus definitions. There are two ways to do this:
        • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
        • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

          Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
      2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
      3. Run a full system scan.
      4. Delete all files that NAV detects as W32.Yaha.E@mm.


      Writeup By: Douglas Knowles