Ransom.Win32.NEMTY.THIOIAI

 Analysis by: Henry Alarcon Jr.

 ALIASES:

RDN/Generic.hra (McAfee), Trojan.Ransom.Nemty (ALYac), Program:Win32/Uwamson.A!ml (Microsoft)

 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 encrypts files found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

1,198,936 bytes

File Type:

EXE

File Compression:

CAB

Memory Resident:

Yes

Initial Samples Received Date:

09 Sep 2019

Payload:

Connects to URLs/IPs, Downloads files, Deletes files, 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:

  • %User Temp%\IXP000.TMP\temp ← encrypted %User Temp%\IXP000.TMP\ironman.exe
  • {Encrypted File Directory}\_NEMTY_{7 random characters}_-DECRYPT.txt ← ransom notes
  • %User Temp%\IXP000.TMP\iron.bmp
  • %User Temp%\iron.txt ← extracted code from image {iron.bmp}

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

It drops and executes the following files:

  • %User Temp%\IXP000.TMP\temp.exe
  • %User Temp%\IXP000.TMP\ironman.exe ← detected as Trojan.Win32.INJECTOR.MV

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

It adds the following processes:

  • %System%\cmd.exe /c vssadmin.exe delete shadows /all /quiet & bcdedit /set {default} bootstatuspolicy ignoreallfailures & bcdedit /set {default} recoveryenabled no & wbadmin delete catalog -quiet & wmic shadowcopy delete
  • %User Profile%\TorDir\Tor\tor.exe ← TOR Browser
  • %System%\cmd.exe /c "{Encrpyted File Directory}\_NEMTY_{7 random characters}_-DECRYPT.txt"

(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).)

It creates the following folders:

  • %User Profile%\TorDir ← folder of extracted TOR Browser {%User Profile%\tor.zip}
  • %User Temp%\IXP000.TMP

(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).. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp 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

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
wextract_cleanup0 = rundll32.exe %System%\advpack.dll,DelNodeRunDLL32 "%User Temp%\IXP000.TMP\"

Other System Modifications

This Ransomware deletes the following files:

  • %User Temp%\IXP000.TMP\temp.exe
  • %User Temp%\IXP000.TMP\temp
  • %User Profile%\tor.zip
  • %User Temp%\IXP000.TMP\iron.bmp
  • %User Temp%\iron.tx

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 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).)

Download Routine

This Ransomware accesses the following websites to download files:

  • https://{BLOCKED}t.{BLOCKED}ject.org/torbrowser/{BLOCKED}.5.4/tor-win32-0.4.0.5.zip ← TOR Browser

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 does the following:

  • It connects to the following URL(s) to get the affected system's IP address and location:
    • http://api.{BLOCKED}y.org/
    • http://api.{BLOCKED}p.com/v2/free/{Affected system IP}/countryName
      • It terminates itself in the affected system if the return of the IP address location is any of the following:
        • Russia
        • Belarus
        • Kazakhstan
        • Tajikistan
        • Ukraine
  • It installs TOR Browser on the affected system.

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • Removable Drive
  • Network Drive
  • Fixed Drive

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

  • nemty
  • log
  • cab
  • cmd
  • com
  • cpl
  • xe
  • ini
  • dll
  • lnk
  • url
  • ttf
  • DECRYPT.txt

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

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

It renames encrypted files using the following names:

  • {encrypted file}._NEMTY_{7 random characters}_

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

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

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.356.01

FIRST VSAPI PATTERN DATE:

09 Sep 2019

VSAPI OPR PATTERN File:

15.357.00

VSAPI OPR PATTERN Date:

10 Sep 2019

Step 1

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 2

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 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
    • wextract_cleanup0 = rundll32.exe %System%\advpack.dll,DelNodeRunDLL32 %User Temp%\IXP000.TMP\

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.
  • %User Temp%\IXP000.TMP\ironman.exe
  • {Encrypted File Directory}\NEMTY_{7 random characters}_-DECRYPT.txt

Step 6

Search and delete these folders

[ 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 Temp%\IXP000.TMP
  • %User Profile%\TorDir

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.NEMTY.THIOIAI. 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 8

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

Restore encrypted files from backup.


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