Home / malware

PDF

Backdoor:W32/Knockex.A

First posted on 08 April 2011.
Source: SecurityHome

Aliases :

There are no other names known for Backdoor:W32/Knockex.A.

Explanation :

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

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

  Last update 08 April 2011

   

  TOP