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Ransom.Win32.NEMTY.M

February 14, 2020
 Analysis by: Mohammed Malubay
 ALIASES:

Ransom:Win32/Nemty.D(MICROSOFT); HEUR:Trojan.Win32.Zenpak.vho(KASPERSKY); Trojan-Ransom.Nemty(IKARUS);

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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 drops files as ransom note.

  TECHNICAL DETAILS

File Size:

94,208 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Feb 2020

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%\{username}@db-ip[1].txt

(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).)

It adds the following processes:

  • "%System%\cmd.exe" /c vssadmin resize shadowstorage /for={drive letter}: /on={drive letter}: /maxsize=401MB
  • "%System%\cmd.exe" /c vssadmin resize shadowstorage /for={drive letter}: /on={drive letter}: /maxsize=unbounded
  • %System%\cmd.exe /c "%User Profile%\NEMTY_{7 random characters}-DECRYPT.txt"
  • %System%\WindowsPowerShell\v1.0\powershell.exe" -e {base-64 encoded}

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %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 System Modifications

This Ransomware adds the following registry entries:

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

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

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

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/122.55.230.51/countryName

It connects to the following possibly malicious URL:

  • http://ocsp.{BLOCKED}i.goog/gsr2/ME4wTDBKMEgwRjAJBgUrDgMCGgUABBTgXIsxbvr2lBkPpoIEVRE6gHlCnAQUm%2BIHV2ccHsBqBt5ZtJot39wZhi4CDQHjtJ13zfQMBhkWtuM%3D
  • http://ocsp.{BLOCKED}i.goog/gts1d2/MFEwTzBNMEswSTAJBgUrDgMCGgUABBT4YwNSyUnwC88de5a5l4eUO%2BLQewQUsd0yXei3N3LSzlzOJv5HeeIBCOkCEGmJiasGJ4WACgAAAAAJZOI%3D

Ransomware Routine

This Ransomware appends the following extension to the file name of the encrypted files:

  • .NEMTY_{7 random characters}

It drops the following file(s) as ransom note:

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

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.682.05

FIRST VSAPI PATTERN DATE:

13 Feb 2020

VSAPI OPR PATTERN File:

15.683.00

VSAPI OPR PATTERN Date:

14 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.XXPE50FFF033

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

Restart in Safe Mode

[ Learn More ]

Step 5

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 6

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
    • cfg = "{random characters}"
  • In HKEY_CURRENT_USER\Software\NEMTY
    • fid = "NEMTY_{7 random characters}"
  • In HKEY_CURRENT_USER\Software\NEMTY
    • pbkey = "{random characters}"

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.
  • %Cookies%\{username}@db-ip[1].txt
  • {Encrypted Directory}\NEMTY_ {7 random characters}-DECRYPT.txt

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.NEMTY.M. 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 this Knowledge Base page for more information.

Step 9

Restore encrypted files from backup.


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