Ransom.MSIL.SYRK.A

 Analysis by: Warren Adam Sto. Tomas

 ALIASES:

Trojan-Ransom.Win32.Gen.sdl (Kaspersky)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • 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 with specific file extensions. It encrypts files found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

12,849,152 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

29 Jul 2019

Payload:

Drops files, Terminates processes, Displays message/message boxes, Connects to URLs/IPs

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:

  • C:\Users\Default\AppData\Local\Microsoft\-pw+.txt -> contains password
  • C:\Users\Default\AppData\Local\Microsoft\+dp-.txt -> contains password and victim ID
  • C:\Users\Default\AppData\Local\Microsoft\-i+.txt -> contains victim ID

It drops and executes the following files:

  • C:\Users\Public\Documents\cgo46ea565sdfse7.exe -> detected as Ransom.Win32.SYRK.A
    • used by the malware to search and encrypt files by executing a Powershell script
  • C:\Users\Public\Documents\dh35s3h8d69s3b1k.exe -> detected as Trojan.Win32.SYRK.A
    • used in decrypting files, also uses a Powershell script
  • C:\Users\Public\Documents\startSF.exe -> detected as Trojan.Win32.SYRK.A
    • used to move C:\Users\Public\Documents\SydneyFortniteHacks.exe to %User Startup%\SydneyFortniteHacks.exe
  • C:\Users\Public\Documents\DeleteFile.exe -> detected as Trojan.Win32.SYRK.A
    • used to delete files this malware created
  • C:\Users\Public\Documents\delmy.exe -> detected as Trojan.Win32.SYRK.A
    • used to delete the file: %User Startup%\SydneyFortniteHacks.exe
  • C:\Users\Public\Documents\LimeUSB_Csharp.exe -> detected as Worm.MSIL.LIME.AA

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%\SydneyFortniteHacks.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 modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows Defender
DisableAntiSpyware = 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_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = 1

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

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = 0

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

It sets the system's desktop wallpaper to the following image:

  • C:\51875.jpg

Process Termination

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

  • Taskmgr
  • Procmon64
  • ProcessHacker

Other Details

This Ransomware displays the following images:

  • Main display:
  • "Show My ID" button:
  • If password input is correct and "Decrypt my Files" button is clicked:

It does the following:

  • If the timer in the main display times out, it will delete files with .Syrk extension in the following directories:
    • %User Profile%\Desktop
    • %User Profile%\Document
    • %User Profile%\Pictures
  • It pings the following URL:
    • {BLOCKED}94fg5sb3y8l.{BLOCKED}hostapp.com
  • On execution, it will move {current directory}\SydneyFortniteHacks.exe to C:\Users\Public\Documents\SydneyFortniteHacks.exe
  • It sends the following via SMTP:
    • Content:
      • Attachment: C:\Users\Default\AppData\Local\Microsoft\+dp-.txt
      • Subject: ID&Pass
    • To:
      • Host: {BLOCKED}mail.com
      • Email: {BLOCKED}som@gmail.com
  • It has a built in decryptor but it will only work if the input password is correct.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • gif
  • sln
  • docx
  • php
  • psd
  • ico
  • mov
  • xlsx
  • jpg
  • xls
  • doc
  • pdf
  • wav
  • pptx
  • ppt
  • txt
  • png
  • bmp
  • rar
  • zip
  • mp3
  • mp4
  • avi

It encrypts files found in the following folders:

  • %User Profile%

(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).)

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

  • .Syrk

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

  • %Desktop%\Readme_now.txt

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

It leaves text files that serve as ransom notes containing the following text:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.272.06

FIRST VSAPI PATTERN DATE:

02 Aug 2019

VSAPI OPR PATTERN File:

15.273.00

VSAPI OPR PATTERN Date:

03 Aug 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

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%\SydneyFortniteHacks.exe
  • C:\Users\Public\Documents\cgo46ea565sdfse7.exe
  • C:\Users\Public\Documents\dh35s3h8d69s3b1k.exe
  • C:\Users\Public\Documents\startSF.exe
  • C:\Users\Public\Documents\DeleteFile.exe
  • C:\Users\Public\Documents\delmy.exe
  • C:\Users\Public\Documents\LimeUSB_Csharp.exe
  • C:\Users\Public\Documents\SydneyFortniteHacks.exe
  • C:\Users\Default\AppData\Local\Microsoft\-pw+.txt
  • C:\Users\Default\AppData\Local\Microsoft\+dp-.txt
  • C:\Users\Default\AppData\Local\Microsoft\-i+.txt

Step 5

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\Policies\Microsoft\Windows Defender
    • DisableAntiSpyware = 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLUA = 0
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • WallpaperStyle = 1
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • TileWallpaper = 0

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.MSIL.SYRK.A. 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

Reset your Desktop properties

[ Learn More ]

Step 8

Restore encrypted files from backup.


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