Threat Description

Email-Worm:​W32/Zafi.D

Details

Aliases:Email-Worm:​W32/Zafi.D
Category:Malware
Type:Email-Worm
Platform:W32

Summary



This type of worm is embedded in an e-mail attachment, and spreads using the infected computer's e-mailing networks.



Removal


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More

You may wish to refer to the Support Community for further assistance. You may also refer to General Removal Instructions for a general guide on alternative disinfection actions.



Technical Details



Email-Worm:W32/Zafi.D distributes copies of its worm code in an e-mail file attachment. Unlike the first Zafi.A variant, Zafi.D uses e-mail messages that are in English, Italian, Spanish, Russian, Swedish and several other languages. The e-mails contain Christmas wish messages. The attachments are files that use PIF, CMD, BAT, COM or ZIP extensions. If executed, the worm can display a decoy message in a message box saying:

  • "Error in packed file!"

The worm code itself is in FSG! packed form 11745 bytes in size. The body unpacks to around 30 KiB of hand-written assembly code.

Infection

When Zafi.D is started it copies itself to the Windows System Directory with a random .DLL name and "Norton Update.exe". The .EXE file is added to the registry key

  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] "Wxp4" = "%System%\Norton Update.exe"

Zafi.D also creates a mutex named "Wxp4" to make sure only one copy of the worm is run at any one time. Several additional files are created in the System Directory with random names and the .DLL extension. The worm keeps its internal data in those. Zafi.D enumerates all the directories in the system and copies itself to the ones that contain 'share', 'upload' or 'music' in their name, using the file names "winamp 5.7 new!.exe" or "ICQ 2005a new!.exe".

Payload

Zafi.D terminates any application that has the words 'firewall' or 'virus' in it. These files are overwritten with a copy of the worm. Several Windows tools, like Task Manager, Registry Editor are disabled when the worm is active. Zafi.D opens these files with exclusive locking to prevent anything else from opening them. Zafi.D has a backdoor that listens on port 8181. The worm can upload and execute file using the backdoor.

Propagation

Zafi.D looks into the Windows Address Book and different files and tries to gather all e-mail addresses listed. Files with the following extensions are checked:

  • htm
  • wab
  • txt
  • dbx
  • tbb
  • asp
  • php
  • sht
  • adb
  • mbx
  • eml
  • pmr
  • fpt
  • inb

Using its own SMTP engine the worm sends messages to the harvested e-mail addresses, with its infectious code attached. The messages can be n many different languages. It can use different SMTP relays for sending its messages depending on the language. For email addresses in the following country domains, the worms sends messages in the respective country's language:

  • .hu - Hungarian
  • .sp
  • .ru - Russian
  • .dk - Danish
  • .ro - Romanian
  • .se - Swedish
  • .no - Norwegian
  • .fi - Finnish
  • .lt - Lithuanian
  • .pl - Polish
  • .pt - Portuguese
  • .de - German
  • .nl - Dutch
  • cz - Czech
  • .fr - French
  • .it - Italian
  • .mx - Mexican
  • .at - Austrian
  • .es - Spanish

The message is a simple christmas wish. Following text is an example of english message:

  • Sender: Pamela M. Subject: Merry Christmas! Happy HollyDays! :) [Sender]

The Sender name is used as a fallback if the email address doesn't have it.Other language versions are as follows

  • Sender: T. MariaSubject: boldog karacsony...Kellemes Unnepeket!:) [Sender]
  • Sender: N. FernandezSubject: Feliz Navidad!Feliz Navidad!:) [Sender]
  • Sender: V. TatyanaSubject: ecard.ru:) [Sender]
  • Sender: V. JensenSubject: Christmas Kort!Glaedelig Jul!:) [Sender]
  • Sender: J. AnderssonSubject: Christmas Vykort!God Jul!:) [Sender]
  • Sender: M. EmmaSubject: Christmas Postkort!God Jul!:) [Sender]
  • Sender: M. VirtanenSubject: Christmas postikorti!Iloista Joulua!:) [Sender]
  • Sender: C. LinaSubject: Christmas Atviruka!Naulieji Metai!:) [Sender]
  • Sender: S. EwaSubject: Christmas - Kartki!Wesolych Swiat!:) [Sender]
  • Sender: H. IreneSubject: Weihnachten card.Fröhliche Weihnachten!:) [Sender]
  • Sender: R. CornelSubject: Prettige Kerstdagen!Prettige Kerstdagen!:) [Sender]
  • Sender: V. DusanSubject: Christmas pohledniceVeselé Vánoce! :) [Sender]
  • Sender: J. MartinSubject: Joyeux Noel!Joyeux Noel!:) [Sender]
  • Sender: T. AntonioSubject: Buon Natale!Buon Natale!:) [Sender]

The worm includes a small visible gif attachement in the messages.The actual worm attachment name is composed of several parts:

  • The word "postcard" in the respective language
  • Random numbers
  • Some of the extensions .pif, .cmd, .bat, .com or .zip.

Sometimes the filename can start with "link", "christmas" or "index".

The worm does not send emails to addresses that contain any of these strings:

  • yaho
  • google
  • win
  • use
  • info
  • help
  • admi
  • webm
  • micro
  • msn
  • hotm
  • suppor
  • syman
  • viru
  • trend
  • secur
  • panda
  • cafee
  • sopho
  • kasper





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