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RANSOM_PEYDAY.A

August 09, 2017
 Analysis by: Martin Xavier Co
 ALIASES:

Trojan:Win32/Dynamer!rfn (Microsoft); W32/Kryptik.FVHB!tr (Fortinet)

 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:

Dropped by other malware, Downloaded from the Internet


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 modifies Internet Explorer security settings. This puts the affected computer at greater risk, as it allows malicious URLs to be accessed by the computer.

  TECHNICAL DETAILS

File Size:

375,296 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Aug 2017

Payload:

Displays message/message boxes, Encrypts 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:

  • %Application Data%\Microsoft\d6cl\stcfg.bin
  • %Application Data%\Microsoft\d6cl\how_to_decrypt_files.hta
  • %Application Data%\Microsoft\d6cl\publickey.bin
  • %Application Data%\Microsoft\d6cl\SwapBuffers\swp_buf0.tmp
  • %Application Data%\Microsoft\d6cl\SwapBuffers\swp_buf1.tmp

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 drops and executes the following files:

  • %Application Data%\Microsoft\d6cl\d6cl.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.)

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
d6cl = %Application Data%\Microsoft\d6cl\d6cl.exe

Web Browser Home Page and Search Page Modification

This Ransomware modifies Internet Explorer zone settings.

Other Details

This Ransomware does the following:

  • This ransomware encrypts files, but does not rename them.

NOTES:

Executing %Application Data%\Microsoft\d6cl\how_to_decrypt_files.hta, the ransomware will display the following ransom note:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.580.04

FIRST VSAPI PATTERN DATE:

07 Aug 2017

VSAPI OPR PATTERN File:

13.581.00

VSAPI OPR PATTERN Date:

08 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

Scan your computer with your Trend Micro product to delete files detected as RANSOM_PEYDAY.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 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.
  • %Application Data%\Microsoft\d6cl\d6cl.exe
  • %Application Data%\Microsoft\d6cl\stcfg.bin
  • %Application Data%\Microsoft\d6cl\how_to_decrypt_files.hta
  • %Application Data%\Microsoft\d6cl\publickey.bin
  • %Application Data%\Microsoft\d6cl\SwapBuffers\swp_buf0.tmp
  • %Application Data%\Microsoft\d6cl\SwapBuffers\swp_buf1.tmp
 

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
    • d6cl = %Application Data%\Microsoft\d6cl\d6cl.exe

Step 6

Restore encrypted files from backup.


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