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RANSOM_CYRON.A

August 30, 2017
 ALIASES:

Mal/Cyronon-A (SOPHOS LITE); Trojan.RansomKD.5871488 (BITFENDER)

 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.

  TECHNICAL DETAILS

File Size:

241,152 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Aug 2017

Payload:

Displays windows, Encrypts files, Locks screen

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:

  • %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe
  • %AppDataLocal%\Microsoft\Windows\svchwost.exe

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It terminates itself if it finds the following processes in the affected system's memory:

  • vmplayer
  • VirtualBox
  • SandmoxieRpcSs

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
svchwost = %AppDataLocal%\Microsoft\Windows\svchwost.exe

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\explorer.exe

HKEY_CURRENT_USER\taskmgr.exe

HKEY_CURRENT_USER\utilman.exe

HKEY_CURRENT_USER\notepad.exe

HKEY_CURRENT_USER\regedit.exe

HKEY_CURRENT_USER\cmd.exe

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Image File Execution Options\explorer.exe
Debugger = %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe

HKEY_LOCAL_MACHINE\Software\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Image File Execution Options\taskmgr.exe
Debugger = %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe

HKEY_LOCAL_MACHINE\Software\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Image File Execution Options\utilman.exe
Debugger = %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe

HKEY_LOCAL_MACHINE\Software\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Image File Execution Options\notepad.exe
Debugger = %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe

HKEY_LOCAL_MACHINE\Software\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Image File Execution Options\regedit.exe
Debugger = %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe

HKEY_LOCAL_MACHINE\Software\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Image File Execution Options\cmd.exe
Debugger = %ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe

File Infection

This Ransomware avoids infecting the following files:

  • desktop.ini

Process Termination

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

  • taskmgr.exe
  • explorer.exe

Ransomware Routine

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

  • .CYRON

NOTES:

It shows the following lockscreen upon execution:

The following message box will show if you try to close the lockscreen window:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.610.08

FIRST VSAPI PATTERN DATE:

22 Aug 2017

VSAPI OPR PATTERN File:

13.611.00

VSAPI OPR PATTERN Date:

23 Aug 2017

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • svchwost = "%AppDataLocal%\Microsoft\Windows\svchwost.exe"
  • In HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\explorer.exe
    • Debugger = "%ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe"
  • In HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\taskmgr.exe
    • Debugger = "%ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe"
  • In HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\utilman.exe
    • Debugger = "%ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe"
  • In HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\notepad.exe
    • Debugger = "%ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe"
  • In HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\regedit.exe
    • Debugger = "%ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe"
  • In HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\cmd.exe
    • Debugger = "%ProgramData%\Microsoft\Windows\Templates\lr4aw4309slk49slk4j9sl456y.exe"

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.

  • HKEY_CURRENT_USER\explorer.exe
  • HKEY_CURRENT_USER\taskmgr.exe
  • HKEY_CURRENT_USER\utilman.exe
  • HKEY_CURRENT_USER\notepad.exe
  • HKEY_CURRENT_USER\regedit.exe
  • HKEY_CURRENT_USER\cmd.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CYRON.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

Restore encrypted files from backup.


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