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Dumaru.Z


Aliases:


Dumaru.Z
W32.Dumaru.Z@mm

Malware
Worm
W32

Summary

A new variant of the Dumaru worm family has been found in the wild on 25th of January, 2004.

This variant of the worm is really similar to the Y variant with the following differences:

  • The FTP backdoor has been removed
  • The TCP bouncer proxy has been removed
  • The code has been reorganized internally
  • This variant downloads a trojan which is detected as TrojanDropper.Win32.Small.aw by F-Secure Anti-Virus


Disinfection & Removal

Dumaru.Z can be removed manually by performing the following steps:

  • 1, Delete the registry value:
    • HKLM\Software\Microsoft\Windows\CurrentVersion\Run\load32
  • 2, Delete the files:
    • %SysDir%\l32x.exe
    • %SysDir%\vxd32v.exe
    • dllxw.exe
    • from the Starup Directory
  • 3, Restore 'system.ini' to
    [Boot]
     Shell=explorer
    
    
  • 4, Restart the computer


Technical Details


System Infection

Upon execution Dumaru.Z installs several copies of itself to the computer:

  • 'l32x.exe' to the Windows System Directory which is added to the registry as
    HKLM\Software\Microsoft\Windows\CurrentVersion\Run\load32
    
    
  • 'dllxw.exe' is copied to the current users' Startup Directory.
  • 'vxd32v.exe' to the Windows System Directory which is added to the system.ini:
    [Boot]
     Shell=explorer vxd32v.exe
    
    

Email Propagation

Dumaru.Z uses its own SMTP engine to send emails. The SMTP engine performs a direct name service lookup on the target domain so it does not depend on the infected computer's email server settings.

To collect email addresses the worm recursively searches through all the directories on the computer and looks for files that could contain email addresses:

'.htm'
 '.wab'
 '.html
 '.dbx'
 '.tbb'
 '.abd'


Going through the list of collected addresses Dumaru.Z sends emails with infected attachments that have to following characteristics:

From: "Elene" <F*CKENSUICIDE@HOTMAIL.COM>
To: <user@targeted.somewhere>
Subject: Important information for you. Read it immediately !
Body: Here is my photo, that you asked for yesterday.
Attachment: myphoto.zip



Payloads

Dumaru.Z - just like it's earlier variants - comes with capabilities to steal sensitive user data:

  • user's POP3 password
  • clipboard data
  • Protected Storage Data
  • User credentials and key log data of visits to www.e-gold.com

The collected data is sent to a predefined email address.


Trojan Downloader

Dumaru.Z has a function that downloads a trojan from a predefined location and places it to 'nvidia32.exe' to the Windows Directory.

The downloaded file is then executed to activate the trojan.



Detection

Detection in F-Secure Anti-Virus was published on January 26th, 2004 in update:

Detection Type: PC
Database: 2004-01-26_01



Description Created: Gergely Erdelyi and Katrin Tocheva, 25th of January, 2004
Technical Details: Gergely Erdelyi, 26th of January, 2004



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