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Ransom.Win32.DHARMA.AB

January 26, 2019
 Analysis by: Cris Nowell Pantanilla
 PLATFORM:

Windows

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • 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:

467,968 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Jan 2019

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 Startup%\{malware filename upon execution}
  • %Common Startup%\{malware filename upon execution}
  • %System%\{malware filename upon execution}

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.. %Common Startup% is the startup folder for all users, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003, or C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It adds the following processes:

  • cmd.exe /c vssadmin delete shadows /all /quiet
  • mode con cp select=1251

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
{malware filename} = %System%\{malware filename}

Ransomware Routine

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

  • {original filename}.id-{ID}.[ra{BLOCKED}ldupon@aol.com].btc

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

  • {Path of encrypted files}\FILES ENCRYPTED.txt
  • %User Startup%\Info.hta

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.770.08

FIRST VSAPI PATTERN DATE:

24 Jan 2019

VSAPI OPR PATTERN File:

14.771.00

VSAPI OPR PATTERN Date:

25 Jan 2019

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 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\Run
    • {malware filename} = %System%\{malware filename}

Step 5

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.
%User Startup%\{malware filename upon execution}
%Common Startup%\{malware filename upon execution}
%System%\{malware filename upon execution}
{Path of encrypted files}\FILES ENCRYPTED.txt
%User Startup%\Info.hta

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.DHARMA.AB. 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 7

Restore encrypted files from backup.


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