1. Symantec/
  2. Security Response/
  3. W32.Yaha.C@mm


May 13, 2002
February 13, 2007 11:39:35 AM
Also Known As:
W32/Yaha.gen [McAfee], WORM_YAHA.C [Trend], I-Worm.Lentin.d [AVP], Win32.Yaha.C [CA], W32/Yaha-C [Sophos]
Systems Affected:
CVE References:

W32.Yaha.C@mm is a mass-mailing worm that sends 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 following file:

%Windows%\[six random numbers][six random numbers].dll

For instance, 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 following strings and then shaking the desktop to make it look like a screensaver:
  • U r so cute today #!#!
  • True Love never ends
  • I like U very much!!!
  • U r My Best Friend

The worm calculates 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, f*cker

    .com, .org, .net

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

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

W32.Yaha.C@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", "¯"

The body will be:

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



followed by:
    [text that is gathered from .doc and .txt files on the infected machine]
    Check the attachment too..
    <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>
    Hi Dear
    Check the Attachement ..
    See u
    [Infected 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 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".

    * 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 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 also randomly use of the Incorrect MIME header exploit, which allows automatic execution of the worm on unpatched systems.

Depending upon the name of the Recycled folder, the worm either copies itself to that folder or to the Windows (or WINNT) directory. The file name consists of six random numbers. The worm configures itself to execute each time an .exe file is executed by changing the default value of the following registry key:



"[WormName]" %1 %*

It also creates a randomly named text file in the Windows directory. For instance, [Random File Name].txt. The file contains the text:
    <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>

    Author :H^H,h2h@achayans.com
    Origin :India,Kerala

    I like Klez,Sircam,But i hate the bullsh*t payloads

    Is i am a good coder?? still i have dout huhh!!!

    Beware Indian Hackers..Tomarrow is ours!!!

    <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>> <<<>>>
The worm also sends a message to one of the following addresses:
    98471[six random numbers]@escotelmobile.com
    98460[six random numbers]@bplmobile.com

with the following characteristics:
    Subject: Beware Indian Hackers!!!!
    Body: We r the Great Indians, Enjoy My w32/yaha!!! By H^H
The worm also makes use of its own SMTP Engine. It attempts to use the infected user's default SMTP server to send mail. If it cannot find that information, then it uses one of many smtp server addresses hardcoded into the worm.

NOTE: None of the above mass-mailing characteristics could be reproduced in the lab environment.


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: Douglas Knowles
Summary| Technical Details| Removal

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