Analysis by: Joshua John Bantayan


Trojan.Win32.Udochka.kb (KASPERSKY); Trojan-Ransom.FileCrypter (IKARUS)




  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes


Infection Channel: Downloaded from the Internet

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.


File Size: 28,160 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 04 Jan 2021
Payload: Encrypts files, Displays message/message boxes

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.


This Ransomware drops the following files:

  • %Application Data%\ecdh_pub_k.bin

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Ransomware does the following:

  • Empties Recycle Bin Contents.
  • Uses Windows Restart Manager to unlock files it will encrypt.
  • Encrypts all fixed and removable drives.
  • It encrypts files from network shares.

It accepts the following parameters:

  • -lan -> Encrypt Network Shares

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file path:

  • Windows
  • Windows.old
  • Tor Browser
  • Internet Explorer
  • Google
  • Opera
  • Opera Software
  • Mozilla
  • Mozilla Firefox
  • $Recycle Bin
  • ProgramData
  • All Users
  • autorun.inf
  • boot.ini
  • bootfont.bin
  • bootsect.bak
  • bootmgr
  • bootmgr.efi
  • bootmgfw.efi
  • desktop.ini
  • iconcache.db
  • ntldr
  • ntuser.dat
  • ntuser.dat.log
  • ntuser.ini.
  • thumbs.db
  • ecdh_pub_k.bin
  • Program Files
  • Program Files (x86)
  • vasa_dbg.txt

It appends the following extension to the file name of the encrypted files:

  • .__NIST_K571__

It leaves text files that serve as ransom notes containing the following text:

  • {Encrypted directory}\DECR.TXT


Minimum Scan Engine: 9.800
VSAPI OPR PATTERN File: 16.457.03
VSAPI OPR PATTERN Date: 01 Jan 2021

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    • Troj.Win32.TRX.XXPE50FFF039

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Identify and terminate files detected as Ransom.Win32.BABUK.THAODBA

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 5

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Application Data%\ecdh_pub_k.bin
  • {Encrypted directory}\DECR.TXT

Step 6

Restore encrypted files from backup.

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