Analysis by: Ryan Paolo Maglaque
ALIASES:

Trojan-Ransom.MSIL.Agent.yh(Kaspersky);Ransom:Win32/Genasom(Microsoft)

 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: 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.

  TECHNICAL DETAILS

File Size: 1,132,544 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 20 Apr 2017
Payload: Encrypts files, Drops 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:

  • %Desktop%\Beni Oku.txt ← Ransom Note
  • %User Profile%\Documents\Beni Oku.txt ← Ransom Note
  • %User Profile%\Documents\images.jpg ← used as wallpaper
  • {Original File Name and Extension}.manifest.xml ← Encryption info

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop 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.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Other System Modifications

This Ransomware changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Profile%\Documents\images.jpg

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

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperPozisyon = 1

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = 0

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

Other Details

This Ransomware renames encrypted files using the following names:

  • {Original File Name and Extension}.encrypted

It does the following:

  • Avoids encrypting the following file extensions:
    • .encrypted
    • .xml
  • Encrypts files in the following directories:
    • C:\Users\{UserName}\Documents
    • C:\Users\{UserName}\Pictures
    • C:\Users\{UserName}\Downloads
    • C:\Users\{UserName}\Desktop
    • D:\

NOTES:

Content of the ransom note:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.356.02
FIRST VSAPI PATTERN DATE: 22 Apr 2017
VSAPI OPR PATTERN File: 13.357.00
VSAPI OPR PATTERN Date: 23 Apr 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

Reset your Desktop properties

[ 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.  
  • %Desktop%\Beni Oku.txt
  • %User Profile%\Documents\Beni Oku.txt
  • %User Profile%\Documents\images.jpg
  • {Original File Name and Extension}.manifest.xml

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_MEDLINZ.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 6

Restore encrypted files from backup.


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