Ransom.Win32.NEMTY.C

November 06, 2019
 Analysis by: Jemimah Mae Molina
 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: 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.

It connects to certain websites to send and receive information.

It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

243,704 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

26 Sep 2019

Payload:

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

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 copies of itself into the affected system:

  • %User Profile%\AdobeUpdate.exe

(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 drops the following files:

  • %Cookies%\{BLOCKED}ser_732@db-ip[1].txt

It adds the following processes:

  • cmd /c %User Profile%\_NEMTY_{7 random characters}_-DECRYPT.txt → opens ransom note
  • vssadmin delete shadows /all /quiet → deletes shadow copies
  • notepad %User Profile%\_NEMTY_{7 random characters}_-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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • just_a_game

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\Software\NEMTY

It adds the following registry entries:

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

HKEY_CURRENT_USER\Software\NEMTY
pbkey = "{random characters}"

HKEY_CURRENT_USER\Software\NEMTY
cfg = "{random characters}"

HKEY_CURRENT_USER\Software\NEMTY
akey = "{random characters}"

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 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/122.55.230.51/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}y.hk/public/gate?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

It adds the following scheduled tasks:

  • Task name: _NEMTY_{7 random characters}_
    Trigger: At log on
    Task to be run: %User Profile%\AdobeUpdate.exe

(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).)

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

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:

15.392.05

FIRST VSAPI PATTERN DATE:

26 Sep 2019

VSAPI OPR PATTERN File:

15.393.00

VSAPI OPR PATTERN Date:

27 Sep 2019

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.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

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\NEMTY
    • fid = _NEMTY_{7 random characters}_
  • In HKEY_CURRENT_USER\Software\NEMTY
    • pbkey = {random characters}
  • In HKEY_CURRENT_USER\Software\NEMTY
    • cfg = {random characters}
  • In HKEY_CURRENT_USER\Software\NEMTY
    • akey = {random characters}

Step 6

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

  • _NEMTY_{7 random characters}_ - %User Profile%\AdobeUpdate.exe

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

Step 7

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.
  • %User Profile%\AdobeUpdate.exe
  • %Cookies%\dyituser_732@db-ip[1].txt
  • {Encrypted Directory}\_NEMTY_{7 random characters}_-DECRYPT.txt

Step 8

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.NEMTY.C. 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 9

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 10

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 11

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 12

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


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