Ransom.Win32.NEMTY.THBOCBO

 Analysis by: Jay Bradley Nebre

 ALIASES:

RDN/Ransom.gn (McAfee); Trojan.Win32.Zenpak.lan (Kaspersky); Mal/GandCrab-G (Sophos)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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.

It connects to certain websites to send and receive information.

It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

283,648 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

29 Jan 2020

Payload:

Connects to URLs/IPs, Drops files, Encrypts files, Terminates processes, 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.

Installation

This Ransomware adds the following processes:

  • cmd.exe/c vssadmin resize shadowstorage /for=A: /on=A: /maxsize=401MB;
  • cmd.exe/c vssadmin resize shadowstorage /for=A: /on=A: /maxsize=unbounded;
  • cmd.exe/c vssadmin resize shadowstorage /for=C: /on=C: /maxsize=401MB;
  • cmd.exe/c vssadmin resize shadowstorage /for=C: /on=C: /maxsize=unbounded;
  • cmd.exe/c vssadmin resize shadowstorage /for=D: /on=D: /maxsize=401MB;
  • cmd.exe/c vssadmin resize shadowstorage /for=D: /on=D: /maxsize=unbounded;
  • cmd.exe/c vssadmin resize shadowstorage /for=F: /on=F: /maxsize=401MB;
  • cmd.exe/c vssadmin resize shadowstorage /for=F: /on=F: /maxsize=unbounded;
  • "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -e {Base64 command};
  • cmd.exe/c "{User Profile}\NEMTY_{7 random characters}-DECRYPT.txt";

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_CURRENT_USER\Software\NEMTY
fid = "_NEMTY_{7 random characters}_"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
daite drobovik = {Malware Name}.exe

Process Termination

This Ransomware terminates the following services if found on the affected system:

  • DbxSvc
  • OracleXETNSListener
  • OracleServiceXE
  • AcrSch2Svc
  • AcronisAgent
  • Apache2.4
  • SQLWriter
  • MSSQL$SQLEXPRESS
  • MSSQLServerADHelper100
  • MongoDB
  • SQLAgent$SQLEXPRESS
  • SQLBrowser
  • CobianBackup11
  • cbVSCService11

It terminates the following processes if found running in the affected system's memory:

  • sql
  • winword
  • wordpad
  • outlook
  • thunderbird
  • oracle
  • excel
  • onenote
  • virtualboxvm

Other Details

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\Software\NEMTY

It connects to the following URL(s) to get the affected system's IP address:

  • www.myexternalip.com
  • http://api.db-ip.com/v2/free/{external ip}/countryName
  • It terminates itself if the location of the IP address is any of the following:
    • Russia
    • Belarus
    • Kazakhstan
    • Tajikistan
    • Ukraine
    • Azerbaijan
    • Armenia
    • Kyrgyzstan
    • Moldova

It connects to the following website to send and receive information:

  • https://{BLOCKED}y10.hk/public/gate.php?data={configuration}

It does the following:

  • It encrypts files in fixed, removable, and network drives.
  • It will not proceed with its routine if found not running on any of the following:
    • Windows 7
    • Windows 8
    • Windows 8.1
    • Windows 10
    • Windows XP

Ransomware Routine

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

  • windows
  • $RECYCLE.BIN
  • rsa
  • NTDETECT.COM
  • ntldr
  • MSDOS.SYS
  • IO.SYS
  • boot.ini
  • AUTOEXEC.BAT
  • ntuser.dat
  • desktop.ini
  • CONFIG.SYS
  • RECYCLER
  • BOOTSECT.BAK
  • bootmgr
  • programdata
  • appdata
  • Common Files
  • TorDir
  • Program Files

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

  • .NEMTY_{7 random characters}

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

  • {Encrypted Directory}\NEMTY_{7 random characters}-DECRYPT.txt

It avoids encrypting files with the following file extensions:

  • .lnk
  • .exe
  • .log
  • .cab
  • .cmd
  • .com
  • .cpl
  • .exe
  • .ini
  • .dll
  • .url
  • .ttf
  • .pif

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.662.02

FIRST VSAPI PATTERN DATE:

03 Feb 2020

VSAPI OPR PATTERN File:

15.663.00

VSAPI OPR PATTERN Date:

04 Feb 2020

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.XXPE50FFF034

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

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software
    • NEMTY

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • daite drobovik = {Malware Name}.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.NEMTY.THBOCBO. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:

Step 7

Enabling Windows Error Recovery

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Windows Error Recovery Screen on Startup by typing the following command:
    bcdedit /set {default} bootstatuspolicy displayallfailures

Step 8

Enabling Volume Shadow Service

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Volume Shadow Service by typing the following command:
    net start vss

Step 9

Enabling Startup Repair

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Startup Repair by typing the following command:
    /bcedit /set {default} recoveryenabled Yes

Step 10

Restore encrypted files from backup.

NOTES:

Restoring Backup Catalog

  1. Run the command prompt (cmd.exe) as administrator.
  2. Restore backup catalog using the following command:
    wbadmin restore catalog


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