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  4. Backdoor:W32/Knockex.A

Backdoor:W32/Knockex.A

Detection Names : Spyware.14597
Dropped:Spyware.14597
Trojan-Dropper:W32/Knockex.A
Trojan-Downloader:W32/Knockex.A
Gen:Variant.Kazy.17250
Backdoor:W32/Knockex.A
Trojan.Generic.KDV.171682
Rootkit:W32/Knockex.A
Trojan.Downloader.Agent.ZBU
Spyware:W32/Inet.B
Adware:W32/MyWebSearch.AG
Adware:W32/MyWebSearch.AF
Adware:W32/MyWebSearch.AH
Spyware:W32/Inet.A
Adware:W32/Zwangi.O
Category:Malware
Type:Backdoor
Platform:W32

Summary

A remote administration utility that bypasses normal security mechanisms to secretly control a program, computer or network.

Disinfection

To remove the backdoor program and other malwares, allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.

To remove the installed adwares, uninstall the following programs from the Windows 'Add/Remove Programs' menu:

  • "Homepage Protection Service" - uninstaller of MYCLEARSEARCH-SETUP.EXE
  • "Inet Support Services" - uninstaller of INET.EXE
  • " BrowserSeek 1.0 build 171 powered by FIRST SEARCHBAR" - uninstaller of BRAND.EXE (as of this writing)

Additional Details

Backdoor:W32/Knockex.A is a backdoor program dropped as part of the payload of a Nullsoft installer (NSIS) program detected as Trojan-Dropper:W32/Knockex.A.

The Nullsoft installer contains the following sub-installers:

  • OfferApp-2529.exe - detected either as Trojan-Downloader:W32/Knockex.A or Gen:Variant.Kazy.17250
  • OfferApp-2526.exe - detected as Spyware:W32/Inet.B

These installers will themselves install multiple installers, which in turn install malware, adware and spyware programs. Among the installed programs is Backdoor:w32/Knockex.A.

 

First Installer Dropped - OfferApp-2529.exe

As of this writing, the first installer dropped by Trojan-Dropper:W32/Knockex.A, OfferApp-2529.exe, downloads and executes a backdoor with rootkit capabilities. The backdoor is detected either as Backdoor:W32/Knockex.A or Trojan.Generic.KDV.171682.

Upon execution, the backdoor program drops the following files:

  • %systemdir%\cssrss.exe
    A copy of the downloaded backdoor program.
  • %systemdir%\nso12k.sys
    A rookit driver (detected either as Rootkit:W32/Knockex.A or Trojan.Downloader.Agent.ZBU) that hides the backdoor program

The backdoor program uses the following launch points:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    "WMDM PMSP Service" = %systemdir%\cssrss.exe
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Driver - service launch point of nso12k.sys

Second Installer Dropped - OfferApp-2526.exe

 

At the same time the OfferApp-2529.exe file is downloading and executing the backdoor, the second installer file, OfferApp-2526.exe, is executing the following installers:

  • myclearsearch-setup.exe
    Installer of MyWebSearch/CreativeToolbar Adware
    Detected as Adware:W32/MyWebSearch.AG
  • inet.exe
    Installer of iNetMedia Adware
    Detected either as Spyware:W32/Inet.A or Spyware.14597
  • brand.exe
    Web Installer/downloader of BrowserSeek/Zwangi Adware
    Detected as Adware:W32/Zwangi.O

When the installers listed are executed, their payloads are installed as separate, independent programs.


Second level of installers from OfferApp-2526.exe

  • myclearsearch-setup.exe
    The myclearsearch-setup.exe file drops the following components:
    • %programdir%\MyClearSearch\MyClearSearchSvc.exe - detected as Adware:W32/MyWebSearch.AF
    • %programdir%\MyClearSearch\ShowMsg.exe - detected as Adware:W32/MyWebSearch.AH
    • %programdir%\MyClearSearch\uninstall.exe - uninstaller component.

    The myclearsearch-setup.exe file then creates the following service launch point:

    • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MyClearSearch Helper Service

    And also creates the following registry keys:

    • HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\SearchScopes
    • HKEY_LOCAL_MACHINE\SOFTWARE\MyClearSearch
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Homepage Protection Service

    During installation, the program will also modify the start page for the Internet Explorer web browser:

    • HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
      "Start Page" = "http://myclearsearch.com/"
  • inet.exe

    When OfferApp-2526.exe is executed, it instructs the inet.exe file installer to download a file from a remote site and install it to the path "C:\Program". During this process, the installer creates the following service launch point:

    • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\inetUpServ

    It will also create a (functional) uninstallation setting:

    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\inet
  • Brand.exe

    Brand.exe is an installer that downloads its own components from a remote site. At the time of writing, the file downloads the following components:

    • %programdir%\BrowserSeek\browserseek.dll
    • %programdir%\BrowserSeek\browserseek.exe
    • %programdir%\BrowserSeek\uninstall.exe

    It creates the following service launch point:

    • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BrowserSeek Service

    And also creates the following registry keys:

    • HKEY_LOCAL_MACHINE\SOFTWARE\BrowserSeek
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\BrowserSeek