Analysis by: Karen Ivy Titiwa
ALIASES:

Trojan.Win32.DelShad.dgg (KASPERSKY); MSIL/DelShad.DGG!tr.ransom(FORTINET)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • 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: 83,968 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 03 Jun 2020
Payload: Encrypts files, Displays message/message boxes

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 adds the following processes:

  • "cmd" /C vssadmin Delete Shadows /All /Quiet
  • netsh.exe netsh advfirewall set currentprofile state off
  • netsh.exe netsh firewall set opmode mode=disable
  • vssadmin Delete Shadows /All /Quiet
  • %System%\svchost.exe -k swprv
  • %System%\sc.exe start w32time task_started

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

Autostart Technique

This Ransomware drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\ransom.exe

(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 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 10(64-bit).)

Other System Modifications

This Ransomware also creates the following registry entry(ies) as part of its installation routine:

HKEY_CURRENT_USER
ransom-782 = {data}

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\swprv
Type = 16

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VSS\Diag
SwProvider_{b5946137-7b9f-4925-af80-51abd60b20d5} =

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VSS\Diag
Registry Writer =

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VSS\Diag
COM+ REGDB Writer =

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VSS\Diag
ASR Writer =

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VSS\Diag
Shadow Copy Optimization Writer =

Other Details

This Ransomware adds and runs the following services:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\swprv

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VSS

Ransomware Routine

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

  • id-{random characters}.[{BLOCKED}s@tuta.io].banks1

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

  • %User Startup%\info.hta
  • {Encrypted directory}\ReadMe.txt

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.912.08
FIRST VSAPI PATTERN DATE: 05 Jun 2020
VSAPI OPR PATTERN File: 15.913.00
VSAPI OPR PATTERN Date: 06 Jun 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.XXPE50FFF035

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
    • ransom-782 = {data}
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\swprv
    • Type = 16
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS
    • Diag

Step 6

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 Startup%\ransom.exe
  • %User Startup%\info.hta
  • {Encrypted directory}\ReadMe.txt

Step 7

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 8

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

Step 9

Restore encrypted files from backup.


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