Analysis by: Patrick Angelo Roderno
ALIASES:

Ransom.HiddenTear (NORTON); Mal/Cryptear-A (SOPHOS-LITE); Trojan.RansomKD.5975246 (BITDEFENDER)

 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.

It uses a user interface (UI).

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

  TECHNICAL DETAILS

File Size: 126,592 bytes
File Type: , EXE
Memory Resident: No
Initial Samples Received Date: 26 Aug 2017
Payload: Displays windows, 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.

Other Details

This Ransomware uses the following user interface:

It does the following:

  • Can perform encryption routine on four different directories at the same time
  • Automatically performs the encryption routine on all four directories if executed while the Shift key is pressed
  • Exits and deletes itself only after performing all the encryption routines
  • Can hide itself

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • All drives

It avoids encrypting files with the following strings in their file name:

  • HOW_TO_RECOVER_ENCRYPTED_FILES
  • .hobot2good

It avoids encrypting files found in the following folders:

  • C:\Windows
  • C:\$Recycle.Bin
  • C:\PerfLogs
  • C:\Intel
  • C:\MSOCache
  • C:\Documents and Settings

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

  • .hobot2good

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

  • {Folders containing Encrypted Files}\HOW_TO_RECOVER_ENCRYPTED_FILES.txt

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.658.04
FIRST VSAPI PATTERN DATE: 11 Sep 2017
VSAPI OPR PATTERN File: 13.659.00
VSAPI OPR PATTERN Date: 12 Sep 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

Identify and terminate files detected as RANSOM_MATROSKA.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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.
  • {Folders containing Encrypted Files}\HOW_TO_RECOVER_ENCRYPTED_FILES.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_MATROSKA.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 the following Trend Micro Support pages for more information:

Step 6

Restore encrypted files from backup.


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