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Trojan.DownLoader43.44599

Added to the Dr.Web virus database: 2021-10-15

Virus description added:

Packer: absent

Compilation date: 2020-07-13

  • SHA1 hash: 1a4b8232237651881750911853cf22d570eada9e

Description

The Trojan is written in C++. Used for unauthorized control of an infected computer.

Operating routine

At the beginning, the trojan decrypts the IP addresses and ports of the C&C server using the XOR operation:


import idaapi
 
address = 0x416200
 
for i in xrange(0x7c):
    idaapi.patch_byte(address + i, idaapi.get_byte(address + i) ^ 0xEF)

Decryption result:

#drweb

C&C server—159.65.157.100:443

Communication with it occurs using sockets:

#drweb

#drweb

Depending on the time, the connection to the required C&C server will be selected:

#drweb

Trojan creates file tmp.0 in folder %tmp%, that used as log.

#drweb

Collect information about system:

#drweb

#drweb

#drweb

Trojan.DownLoader43.44599 pushes each value onto a stack before encrypting and sending the collected data. The transferred data looks as follows:


struct computer_info {
    string computer_name;
    string user_name;
    uint32_t major_version;
    uint32_t minor_version;
    uint32_t build_number;
    uint32_t computer_bitness;
    string March01;
    uint32_t code_page_id;
    uint32_t oem_code_page_id;
};

To encrypt the information collected about the system, the AES128 algorithm is used in CBC mode.

The key and initialization vector are embeded inside:

#drweb

The decryption method look as follows:


from Crypto.Cipher import AES
 
key = '\x95\x2B\x2D\xBF\x09\xC5\x2F\x80\xB4\xBC\x47\x27\x29\xB3\x28\x09'
iv = '\x63\x5F\x72\x2A\xBB\xE3\xE8\x95\xF8\xF9\x32\x87\x53\x6A\x77\xFB'
enc = ...
 
decipher = AES.new(key, AES.MODE_CBC, iv)
open('dec', 'wb').write(decipher.decrypt(enc))

The cycle of execution of commands received from the C&C server:

#drweb

Table of commands compiled from the results of this cycle:

Command ID Command
0x51Creating cmd.exe process
0x52Execution command exit in cmd.exe
0x54Command executing в cmd.exe
0x60Creating the flow, that reads, writes and encrypt files.

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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Download by serial number

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.

Download Dr.Web

Download by serial number

  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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