Modified by: Jemimah Mae Molina
ALIASES:

Ransom:Win32/Nemty (Microsoft); RDN/Ransom (McAfee); Trojan-Ransom.Win32.Gen.snw (Kaspersky); Troj/Nemty-A (Sophos); Trojan.Win32.Generic!BT (Sunbelt)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

  TECHNICAL DETAILS

File Size: 187,392 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 22 Aug 2019
Payload: Connects to URLs/IPs, Downloads files, Displays message/message boxes, Encrypts files

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 drops the following files:

  • %Cookies%\{user name}@db-ip[1].txt
  • %User Profile%\_NEMTY_{7 random characters}_.nemty

(Note: %Cookies% is the Internet Explorer browser cookies folder, which is usually C:\Documents and Settings\{user name}\Cookies on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Cookies on Windows Vista and 7, or C:\Users\{user name}\AppData\Local\Microsoft\Windows\INetCookies on Windows 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • cmd /c %User Profile%\NEMTY-DECRYPT.txt → opens ransom note
  • vssadmin delete shadows /all /quiet → deletes shadow copies
  • notepad %User Profile%\NEMTY-DECRYPT.txt → opens ransom note
  • bcdedit /set {default} bootstatuspolicy ignoreallfailures → disables Windows error recovery
  • bcdedit /set {default} recoveryenabled no → disables automatic repair
  • wbadmin delete catalog -quiet → deletes backup catalog
  • wmic shadowcopy delete → deletes shadow copies

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

It creates the following folders:

  • %User Profile%\TorDir → contains extracted TOR Browser

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

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • hate

Download Routine

This Ransomware accesses the following websites to download files:

  • https://dist.{BLOCKED}ject.org/torbrowser/8.5.4/tor-win32-0.4.0.5.zip

It saves the files it downloads using the following names:

  • %User Profile%\tor.zip

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

Other Details

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

  • http://api.ipify.org/
  • http://api.db-ip.com/v2/free/{BLOCKED}.{BLOCKED}.230.51/countryName
    • It terminates itself if the location of the IP address is any of the following:
      • Russia
      • Belarus
      • Kazakhstan
      • Tajikistan
      • Ukraine

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 name:

  • nemty
  • log
  • LOG
  • CAB
  • cab
  • CMD
  • cmd
  • COM
  • com
  • cpl
  • CPL
  • exe
  • EXE
  • ini
  • INI
  • dll
  • DLL
  • lnk
  • LNK
  • url
  • URL
  • ttf
  • TTF
  • DECRYPT.txt

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

  • $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
  • windows
  • Microsoft
  • Common Files

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

  • .nemty

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

  • {Encrypted Directory}\NEMTY-DECRYPT.txt

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.326.05
FIRST VSAPI PATTERN DATE: 27 Aug 2019
VSAPI OPR PATTERN File: 15.327.00
VSAPI OPR PATTERN Date: 28 Aug 2019

Step 1

Trend Micro products with the XGen technology detect this malware as

[ Learn More ]
 
  • Troj.Win32.TRX.XXPE50FFF031

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

Search and delete these files

[ 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.
  • %Cookies%\{user name}@db-ip[1].txt
  • %User Profile%\_NEMTY_{7 random characters}_.nemty
  • {Encrypted Directory}\NEMTY-DECRYPT.txt

Step 5

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Profile%\TorDir

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.NEMTY.A. 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

  • Run the command prompt (cmd.exe) as administrator.
  • Restore backup catalog using the following command:

    wbadmin restore catalog


Did this description help? Tell us how we did.