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ニュース

Trojan.MulDrop36.3931

Added to the Dr.Web virus database: 2026-02-27

Virus description added:

Technical Information

To ensure autorun and distribution
Modifies the following registry keys
  • [HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce] 'WindowsSystemOptimizer' = '<Full path to file>'
Creates or modifies the following files
  • <SYSTEM32>\tasks\systemoptimizer
  • %APPDATA%\microsoft\windows\start menu\programs\startup\windowssystemoptimizer.exe
Modifies file system
Creates the following files
  • %TEMP%\_mei50802\crypto\cipher\_arc4.pyd
  • %TEMP%\_mei50802\crypto\cipher\_salsa20.pyd
  • %TEMP%\_mei50802\crypto\cipher\_chacha20.pyd
  • %TEMP%\_mei50802\crypto\cipher\_pkcs1_decode.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_aes.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_aesni.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_arc2.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_blowfish.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_cast.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_cbc.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_cfb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ctr.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_des.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_des3.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ecb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_eksblowfish.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ocb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ofb.pyd
  • %TEMP%\_mei50802\crypto\hash\_blake2b.pyd
  • %TEMP%\_mei50802\crypto\hash\_blake2s.pyd
  • %TEMP%\_mei50802\crypto\hash\_md2.pyd
  • %TEMP%\_mei50802\crypto\hash\_md4.pyd
  • %TEMP%\_mei50802\crypto\hash\_md5.pyd
  • %TEMP%\_mei50802\crypto\hash\_ripemd160.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha1.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha224.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha256.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha384.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha512.pyd
  • %TEMP%\_mei50802\crypto\hash\_ghash_clmul.pyd
  • %TEMP%\_mei50802\crypto\hash\_ghash_portable.pyd
  • %TEMP%\_mei50802\crypto\hash\_keccak.pyd
  • %TEMP%\_mei50802\crypto\hash\_poly1305.pyd
  • %TEMP%\_mei50802\crypto\math\_modexp.pyd
  • %TEMP%\_mei50802\crypto\protocol\_scrypt.pyd
  • %TEMP%\_mei50802\crypto\publickey\_curve25519.pyd
  • %TEMP%\_mei50802\crypto\publickey\_curve448.pyd
  • %TEMP%\_mei50802\crypto\publickey\_ec_ws.pyd
  • %TEMP%\_mei50802\crypto\publickey\_ed25519.pyd
  • %TEMP%\_mei50802\crypto\publickey\_ed448.pyd
  • %TEMP%\_mei50802\crypto\util\_cpuid_c.pyd
  • %TEMP%\_mei50802\crypto\util\_strxor.pyd
  • %TEMP%\_mei50802\vcruntime140.dll
  • %TEMP%\_mei50802\vcruntime140_1.dll
  • %TEMP%\_mei50802\_asyncio.pyd
  • %TEMP%\_mei50802\_bz2.pyd
  • %TEMP%\_mei50802\_cffi_backend.cp314-win_amd64.pyd
  • %TEMP%\_mei50802\_ctypes.pyd
  • %TEMP%\_mei50802\_decimal.pyd
  • %TEMP%\_mei50802\_hashlib.pyd
  • %TEMP%\_mei50802\_lzma.pyd
  • %TEMP%\_mei50802\_multiprocessing.pyd
  • %TEMP%\_mei50802\_overlapped.pyd
  • %TEMP%\_mei50802\_queue.pyd
  • %TEMP%\_mei50802\_socket.pyd
  • %TEMP%\_mei50802\_ssl.pyd
  • %TEMP%\_mei50802\_uuid.pyd
  • %TEMP%\_mei50802\_wmi.pyd
  • %TEMP%\_mei50802\_zstd.pyd
  • %TEMP%\_mei50802\base_library.zip
  • %TEMP%\_mei50802\libcrypto-3.dll
  • %TEMP%\_mei50802\libffi-8.dll
  • %TEMP%\_mei50802\libssl-3.dll
  • %TEMP%\_mei50802\pyexpat.pyd
  • %TEMP%\_mei50802\python314.dll
  • %TEMP%\_mei50802\pywin32_system32\pywintypes314.dll
  • %TEMP%\_mei50802\select.pyd
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\installer
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\metadata
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\record
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\wheel
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\licenses\license
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\top_level.txt
  • %TEMP%\_mei50802\setuptools\_vendor\jaraco\text\lorem ipsum.txt
  • %TEMP%\_mei50802\unicodedata.pyd
  • %TEMP%\_mei50802\win32\win32crypt.pyd
  • <SYSTEM32>\autoscript.exe
Sets the 'hidden' attribute to the following files
  • <SYSTEM32>\autoscript.exe
  • %APPDATA%\microsoft\windows\start menu\programs\startup\windowssystemoptimizer.exe
Deletes following files that it created itself
  • %TEMP%\_mei50802\base_library.zip
  • %TEMP%\_mei50802\crypto\cipher\_arc4.pyd
  • %TEMP%\_mei50802\crypto\cipher\_chacha20.pyd
  • %TEMP%\_mei50802\crypto\cipher\_pkcs1_decode.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_aes.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_aesni.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_arc2.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_blowfish.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_cast.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_cbc.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_cfb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ctr.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_des.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_des3.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ecb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_eksblowfish.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ocb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_raw_ofb.pyd
  • %TEMP%\_mei50802\crypto\cipher\_salsa20.pyd
  • %TEMP%\_mei50802\crypto\hash\_blake2b.pyd
  • %TEMP%\_mei50802\crypto\hash\_blake2s.pyd
  • %TEMP%\_mei50802\crypto\hash\_ghash_clmul.pyd
  • %TEMP%\_mei50802\crypto\hash\_ghash_portable.pyd
  • %TEMP%\_mei50802\crypto\hash\_keccak.pyd
  • %TEMP%\_mei50802\crypto\hash\_md2.pyd
  • %TEMP%\_mei50802\crypto\hash\_md4.pyd
  • %TEMP%\_mei50802\crypto\hash\_md5.pyd
  • %TEMP%\_mei50802\crypto\hash\_poly1305.pyd
  • %TEMP%\_mei50802\crypto\hash\_ripemd160.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha1.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha224.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha256.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha384.pyd
  • %TEMP%\_mei50802\crypto\hash\_sha512.pyd
  • %TEMP%\_mei50802\crypto\math\_modexp.pyd
  • %TEMP%\_mei50802\crypto\protocol\_scrypt.pyd
  • %TEMP%\_mei50802\crypto\publickey\_curve25519.pyd
  • %TEMP%\_mei50802\crypto\publickey\_curve448.pyd
  • %TEMP%\_mei50802\crypto\publickey\_ec_ws.pyd
  • %TEMP%\_mei50802\crypto\publickey\_ed25519.pyd
  • %TEMP%\_mei50802\crypto\publickey\_ed448.pyd
  • %TEMP%\_mei50802\crypto\util\_cpuid_c.pyd
  • %TEMP%\_mei50802\crypto\util\_strxor.pyd
  • %TEMP%\_mei50802\libcrypto-3.dll
  • %TEMP%\_mei50802\libffi-8.dll
  • %TEMP%\_mei50802\libssl-3.dll
  • %TEMP%\_mei50802\pyexpat.pyd
  • %TEMP%\_mei50802\python314.dll
  • %TEMP%\_mei50802\pywin32_system32\pywintypes314.dll
  • %TEMP%\_mei50802\select.pyd
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\installer
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\licenses\license
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\metadata
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\record
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\top_level.txt
  • %TEMP%\_mei50802\setuptools\_vendor\importlib_metadata-8.7.1.dist-info\wheel
  • %TEMP%\_mei50802\setuptools\_vendor\jaraco\text\lorem ipsum.txt
  • %TEMP%\_mei50802\unicodedata.pyd
  • %TEMP%\_mei50802\vcruntime140.dll
  • %TEMP%\_mei50802\vcruntime140_1.dll
  • %TEMP%\_mei50802\win32\win32crypt.pyd
  • %TEMP%\_mei50802\_asyncio.pyd
  • %TEMP%\_mei50802\_bz2.pyd
  • %TEMP%\_mei50802\_cffi_backend.cp314-win_amd64.pyd
  • %TEMP%\_mei50802\_ctypes.pyd
  • %TEMP%\_mei50802\_decimal.pyd
  • %TEMP%\_mei50802\_hashlib.pyd
  • %TEMP%\_mei50802\_lzma.pyd
  • %TEMP%\_mei50802\_multiprocessing.pyd
  • %TEMP%\_mei50802\_overlapped.pyd
  • %TEMP%\_mei50802\_queue.pyd
  • %TEMP%\_mei50802\_socket.pyd
  • %TEMP%\_mei50802\_ssl.pyd
  • %TEMP%\_mei50802\_uuid.pyd
  • %TEMP%\_mei50802\_wmi.pyd
  • %TEMP%\_mei50802\_zstd.pyd
Network activity
Connects to
  • '<DNS_SERVER>':53
Miscellaneous
Restarts the analyzed sample
Executes the following
  • '<SYSTEM32>\attrib.exe' +h <SYSTEM32>\AutoScript.exe
  • '<SYSTEM32>\schtasks.exe' /create /tn SystemOptimizer /tr "\"<Full path to file>\" --boot" /sc onlogon /rl limited /f /np /ru SYSTEM
  • '<SYSTEM32>\attrib.exe' +h "%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\WindowsSystemOptimizer.exe"

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.

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Download on App Store

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.

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