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Trojan.Encoder.2843

Added to the Dr.Web virus database: 2015-11-02

Virus description added:

SHA1 a72200e7d8918b8d76e74bbb74bdde4ae4f1b8a2

Encryption ransomware that has been distributed via mass mailings since November 2, 2015. The Trojan is disguised as a small file containing a JavaScript script. Once launched, this file extracts from its body an application that ensures the Trojan's running.

The malware adds an encrypted dynamic-link library (.DLL) to the Windows system registry and then injects a small piece of code into explorer.exe. The code loads the file from the registry into the memory, decrypts it, and transfers control to this file. The library is compressed with UPACK and has the size of about 20 KB.

The list of files to be encrypted is stored in the HKCU\Software\Microsoft\Windows\CurrentVersion\Ext\Settings\ registry branch. For every file, Trojan.Encoder.2843 generates a unique key (0x38) consisting of uppercase Latin letters. Files are encrypted with Blowfish ECB (448-byte key); at that, the maximum length of an encrypted data block is 0x14000000. Each encrypted file is appended with the .vault extension.

A session key is encrypted with RSA using CryptoAPI.

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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