Worm:W32/TDSS.BU

Classification

Malware

Worm

W32

Worm:W32/TDSS.BU

Summary

This worm is delivered as a malicious file by the malware Trojan:W32/TDSS.BR. The fake download is itself downloaded from a fake video site.

Removal

Automatic action

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

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Technical Details

Installation

Upon execution of the worm's file, it creates a copy of the file "%System%\msi.dll" as:

  • %Temp%\tmp[randnumber2].tmp

It then modifies this file with 21 bytes at the entry point, in order to load the file, %Temp%\tmp[Randomnumber1].tmp.

To complete loading the file, a series of additional changes must performed:

  • First, the malware deletes the "\knowndlls\msi.dll" section object of the Windows operating system, in order to remove the legitimate msi.dll.
  • The section object is then recreated and linked to the %Temp%\tmp[Randomnumber2].tmp file.
  • It then stops and restarts the "MSISERVER" Windows Service, which subsequently loads the %Temp%\tmp[Randomnumber2].tmp file.

The cumulative effect of these changes cause the file, Temp%\tmp[Randomnumber1].tmp to be loaded as a Windows service.

The worm also creates the following files on Removable and Fixed Drives:

  • [DriveLetter]:\RECYCLER\S-%u-%u-%u-%u-%u-%u-%u.com - copy of itself
  • [DriveLetter]:\autorun.inf

Activity

While active, the worm will attempt to connect to a remote site (see above). Once connected, it receives encrypted data from the remote server, which it then decrypts in order to create and load an executable file as:

  • %windir%\TEMP\tempo-%u.tmp

Registry

The autorun.inf file created during installation contains the following strings:

  • [autorun] ;[random characters] shellexecute="RECYCLER\S-%u-%u-%u-%u-%u-%u-%u.com [DriveLetter]:\" ;[random characters] shell\Open\command="RECYCLER\S-%u-%u-%u-%u-%u-%u-%u.com [DriveLetter]:\" ;[random characters] shell=Open

Network Connections

Attempts to connect with HTTP to:

  • https://94.247.2.107/cgi-bin/generator

Registry Modifications

Creates these keys:

  • HKEY_CLASSES_ROOT\videoshow\CLSID (Default) = "{6BF52A52-394A-11D3-B153-00C04F79FAA6}"

Date Created: 2009-03-26 02:46:56.0

Date Last Modified: 2009-03-26 07:46:55.0