Threat Descriptons



Category :


Type :


Aliases :

W32/Lentin.G@mm, I-Worm.Lentin.H, Lentin.H, Yaha.H


The Yaha.J worm was sent to over 50 different mailing lists on Friday the 13th of December 2002.


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Technical Details

The Yaha.J worm was sent to over 50 different mailing lists on Friday the 13th of December 2002.

The initial emails looked like this:

From: HotGal4U2Fuk@Hotmail.Com
To: member-of-one-of-the-yahoogroups-mailing-list
Subject: joke

 look attach very gooooode

Attachment: love.gif .scr

This Yaha worm variant installs itself to system 3 times, creates a startup key for one of its files in the Registry and also modifies EXE file startup key so its other file could be started every time a user runs an EXE file. When run for the first time, Yaha.J displays a fake error message.

Yaha.J speads itself in email messages with different subjects. It also spams numerous email addresses by sending a message without its attachment there.

When Yaha.J is run for the first time, it displays a fake error message:

 Application initilisation error

Then Yaha.J installs itself to system. It copies itself 3 times to Windows System directory with the following names:

  • NAV32.EXE

Yaha.J sets hidden attribute to all these files, so they are not seen in Windows Explorer with default settings.

Then Yaha.J creates 2 startup keys for the WINREG.EXE file in the System Registry:

  • [HKLM\Software\Microsoft\Windows\CurrentVersion\Run] "winReg" = "%WinSysDir%\winReg.exe"
  • [HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices "winReg" = "%WinSysDir%\winReg.exe"

The %WinSysDir% represents Windows System directory name. Also Yaha.J modifies the default EXE file startup key:

  • [HKCR\exefile\shell\open\command] @ = "%WinSysDir%\Nav32.exe "%1"%*"

This way Yaha.J's files are started not only during Windows startup, but also when a user runs any EXE file.

Yaha.J creates several threads that refresh its Registry keys and continuously restore Yaha.J's files if they are deleted from a hard drive. One of the threads kills processes with the following names:

  • CFINET32
  • LOCKDOWN2000
  • AVP32
  • VSHWIN32
  • NAVAPW32
  • NAVW32
  • NSCHED32
  • SCAN32
  • TDS2-98
  • TDS2-NT
  • RESCUE32
  • NAVLU32
  • PVIEW95
  • F-PROT95
  • PCCWIN98
  • IOMON98
  • FP-WIN
  • NVC95

Yaha.J looks for email addresses in Windows Address Book, cache folders of NET and MSN messengers and in Yahoo Messenger profile folders.

When Yaha.J locates an email address, it browses the domain name, then connects to a DNS server at address and attempts to locate an anonymous SMTP server for that domain.

The message composition routine of this Yaha variant is quite complex. Yaha.J randomly selects fake reply-to addresses, fake names of senders, subjects and attachment names. Here's an example:

A subject of an infected email can be one of the following:

  • Friendship Screensaver Inc.
  • Microsoft Screensavers
  • IBM Screensavers
  • Lover's Scnreensaver
  • Valentine Screensaver
  • Sunrise Screensavers
  • Marcos D'Costa
  • Kevin Mitnick
  • Bill Gates
  • Sexy Screensavers
  • Hardcore Screensavers
  • Accoustic Screensavers
  • Electric Screensavers
  • KOF Screensavers
  • Patriotic Screensavers
  • Enjoy the fragrance of Love
  • Pamela Anderson Screensavers
  • Devon Loves Bill Gates
  • Horny Britney Spears Screensavers
  • Are you in Love
  • You are my best friend
  • Who is your best friend
  • Happy Valentines Day
  • So Sweet
  • Dedicated to kYo-3
  • Leona and Ralph
  • Happy Cristmas
  • Do you love your wife
  • Good Luck
  • Mission Impossible
  • Are you In Love
  • Friendship ScreenSaver
  • Pamela 4 U
  • Still Dreaming..
  • Experience the smooooth music
  • Help someone..
  • Check this
  • Wanna be a hacker ?
  • mAtRiX
  • Missing your best friend ?

A fake sender's name can be one of the following:

  • Paul Smith
  • Bernard Lewis
  • Britney Johnson
  • Susan Sarandon
  • Zeus Gavinson
  • Kevin Mitnick
  • Friendship Screensaver Inc.
  • Passionate
  • Lover's Corner
  • Rick Stenquin
  • Amino Extolden
  • Sweetheart
  • Girl Friends
  • The Great Indians
  • Susy Aminot
  • Gavin Lawson
  • Viivi Josefiina Torronen
  • Carmen Vidal
  • Cathy Stevens
  • Zeusita
  • Love Inc.
  • Dead Man Inc.
  • Dreamz of Love Inc.

A fake sender's email address can be one of the following:


A body of an infected message can look like that:

This email 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 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:
 * Enter your email address in the field provided and click "Unsubscribe


 * Reply to this message with the word "REMOVE" in the subject line.

An infected attachment can have one of the following names:

  • LoverScreenSaver.scr
  • ScreenSaver.scr
  • Honey.scr
  • HotShot.scr
  • NeverMind.scr
  • Escort.scr
  • Love.scr
  • EvilDaemon.scr
  • mAtRiX.scr
  • bestfriend.scr

Also an attachment can have double extension. An extension is selected by Yaha.J from the following list:

  • .pdf .scr
  • .gif .scr
  • .ppt .scr
  • .jpg .scr
  • .doc .scr

Note that there are 23 space characters between these 2 extensions. This is done to hide the second, executable extension.

Yaha.J sends numerous email messages with the above listed body text, but without its attachment to the following addresses:


Yaha.J does not use Iframe exploit in infected messages to start itself automatically. That limits its spreading.

Yaha.J can create zEsT.txt file in Windows directory and whites the following text there:

 r^0^x~X pR3$@Nt$ @Y3rH$.@',0Ah

tHi$ i$ jU$t tH3 b3gInNiNg..

w3 ar3 tH3 gR3@t 1nD1@N$..

 w3 k1cK pAk1 a$$..


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