Analysis by: Rheniel Rhay Ramos
ALIASES:

Ransom.HiddenTear (Malwarebytes); Ransom:MSIL/Ryzerlo.A (Microsoft); Ransom.HiddenTear!g1 (Symantec)

 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

This Ransomware encrypts files found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 88,576 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 16 Oct 2017
Payload: Encrypts files

Installation

This Ransomware drops the following copies of itself into the affected system and executes them:

  • %User Profile%\Videos\skype.exe -> used to decrypt files

(Note: %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.)

It drops the following files:

  • %User Profile%\Documents\decrpt.dll -> encryption key

(Note: %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 Details

This Ransomware displays a pop-up window with the following message:


Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • %User Profile%\Music

(Note: %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.)

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

  • .viiper

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

  • %Desktop%\READ_ME_IMPORTANT.txt

(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.)

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

  • Oops. Your Files has been encrypted and are useless now!
    You just can recover them, if you pay the Amount wich is shown in the Window
    Force Close the Program will result in losing Data forever!

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.726.05
FIRST VSAPI PATTERN DATE: 16 Oct 2017
VSAPI OPR PATTERN File: 13.727.00
VSAPI OPR PATTERN Date: 17 Oct 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

Search and delete these files

[ 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 Profile%\Videos\skype.exe
  • %User Profile%\Documents\decrpt.dll
  • %Desktop%\READ_ME_IMPORTANT.txt

Step 4

Scan your computer with your Trend Micro product to delete files detected as RANSOM_HIDDENTEARVIPER.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 5

Restore encrypted files from backup.


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