Worm:W32/TDSS.BU

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}"