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BAT.Encoder.23

Added to the Dr.Web virus database:2014-08-06
Virus description added:

This is a Trojan program that encrypts files via a legitimate cryptographic tool, named GPG, using BAT scripts. The Trojan penetrates a system with the use of JS.Downloader.300 downloader, which is distributed via mass spam mailings.

The Trojan is a more sophisticated version of BAT.Encoder.2. This modification is mainly distinguished from the predecessor by the fact that the master key is located in the .bat file.

Once the malware is launched, it creates the %temp%\crypta.bin file in order to prevent repeated launch of its own copy. When the malware finishes encryption, it removes this file from the system. Next, the Trojan extracts the public part of its master key, generates a GPG key pair (pubring.gpg and secring.gpg) and saves it to the %temp% folder. After that, it encrypts the private part of the session key to the KEY.PRIVATE file. Thereafter, the Trojan sends its copies to all email addresses found on the infected computer.

For session key encryption, the Trojan uses a key with the ID equal to A3CE7DBE. All encrypted files have an additional extension — keybtc@gmail_com.

In general, files encrypted with BAT.Encoder.23 cannot be decrypted without the private part of the used master key. However, if the master key is known, it is usually possible to perform their decryption.

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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  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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