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Ransom.Win32.MRDEC.MRA

December 28, 2019
 Analysis by: Warren Adam Sto. Tomas
 ALIASES:

Trojan-Ransom.FileCrypter (Ikarus);

 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 drops files as ransom note.

  TECHNICAL DETAILS

File Size:

12,288 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

19 Dec 2019

Payload:

Drops 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:

  • %Windows%\ncler.txt -> contains logging of the malware's activities
  • %Windows%\clerlog.bat -> used to clear logs using wevtutil, delete contents in Recycle Bin, delete shadow copies of ncler.txt
  • %System Root%\Decoding help.hta -> ransom note

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

It drops the following copies of itself into the affected system:

  • %Windows%\searchfiles.exe

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

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\Run
unlock = "%System Root%\Decoding help.hta"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
searchfiles = "%Windows%\searchfiles.exe"

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.[ID]{Random Characters}[ID]

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\DateTime
orsa = "{Hex values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\DateTime
rsa = "{Hex values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.[ID]{Random Characters}[ID]\shell\open\
command
(Default) = "%System%\mshta.exe %System Root%\Decoding help.hta"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
PromptOnSecureDesktop = "0"

(Note: The default value data of the said registry entry is {User Preference}.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = "0"

(Note: The default value data of the said registry entry is {User Preference}.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
ConsentPromptBehaviorAdmin = "0"

(Note: The default value data of the said registry entry is {User Preference}.)

Process Termination

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

  • All processes excluding the following:
    • [System Process]
    • System
    • smss.exe
    • dllhost.exe
    • svchost.exe
    • csrss.exe
    • Microsoft.ActiveDirectory
    • WebServices.exe
    • cmd.exe
    • mstsc.exe
    • find.exe
    • conhost.exe
    • explorer.exe
    • ctfmon.exe
    • lsass.exe
    • services.exe
    • tasklist.exe
    • winlogon.exe
    • wmiprvse.exe
    • msdts.exe
    • bfsvc.exe
    • AdapterTroubleshooter.exe
    • alg.exe
    • dwm.exe
    • issch.exe
    • rundll32.exe
    • spoolsv.exe
    • wininit.exe
    • wmiprvse.exe
    • wudfhost.exe
    • taskmgr.exe
    • rdpclip.exe
    • logonui.exe
    • lsm.exe
    • searchui.exe
    • searchindexer.exe
    • processhacker.exe
    • getpassvord_x64.exe
    • 64.exe
    • 32.exe
    • mshta.exe
    • fontdrvhost.exe
    • sihost.exe
    • pscan24.exe
    • advanced_port_scanner.exe
    • advanced_port_scanner_console.exe
    • pscan24.tmp
    • PSEXESVC.exe
    • diskshadow.exe
    • dfssvc.exe

Other Details

This Ransomware displays the following images:


It does the following:

  • It encrypts files found in all drives including network drives
  • It deletes all shadow copies using the following command:
    • cmd /c vssadmin delete shadows /all

Ransomware Routine

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

  • Decoding help.hta

It avoids encrypting files found in the following folders:

  • Windows

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

  • .[ID]{Random Characters}[ID]

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

  • {Encrypted directory}\Decoding help.hta

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.568.05

FIRST VSAPI PATTERN DATE:

19 Dec 2019

VSAPI OPR PATTERN File:

15.569.00

VSAPI OPR PATTERN Date:

20 Dec 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.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 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\Run
    • unlock = "%System Root%\Decoding help.hta"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • searchfiles = "%Windows%\searchfiles.exe"

Step 6

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.

  • HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.[ID]{Random Characters}[ID]

Step 7

Restore this modified 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\Policies\System
    • PromptOnSecureDesktop = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLUA = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • ConsentPromptBehaviorAdmin = "0"

Step 8

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.
  • %Windows%\ncler.txt
  • %Windows%\clerlog.bat
  • %System Root%\Decoding help.hta

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.MRDEC.MRA. 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 10

Restore encrypted files from backup.

Step 11

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


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