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RANSOM_HIDDENTEARKARMEN.A

March 22, 2017
 Analysis by: John Anthony Banes
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: ransomware

  • Destructiveness: No

  • Encrypted:

  • 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 executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

12,800 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

15 Mar 2017

Payload:

Connects to URLs/IPs, 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.

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\Run
DecryptFiles = C:\Users\{username}\AppData\Local\Temp\decrypt.exe

Dropping Routine

This ransomware drops the following files:

  • C:\Users\{username}\AppData\Local\Temp\id.txt - 15 random characters
  • C:\Users\{username}\AppData\Local\Temp\adr.txt - bitcoin address
  • C:\Users\{username}\AppData\Local\Temp\lnk.txt - server
  • C:\Users\{username}\AppData\Local\Temp\btc.txt - bitcoins to pay
  • C:\Users\{username}\AppData\Local\Temp\del.bat - terminates and deletes decrypt.exe, and deletes the text files

Download Routine

This ransomware accesses the following websites to download files:

  • http://{BLOCKED}.{BLOCKED}.123.78/decrypt.exe

It saves the files it downloads using the following names:

  • C:\Users\{username}\AppData\Local\Temp\decrypt.exe - ransom note and decrypt program

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This ransomware connects to the following website to send and receive information:

  • http://{BLOCKED}.{BLOCKED}.123.78/

It encrypts files with the following extensions:

  • .sql
  • .csv
  • .zip
  • .mdbackup
  • .syncdb
  • .css
  • .js
  • .txt
  • .pdf
  • .doc
  • .docx
  • .exl
  • .kdbx
  • .kdb

It renames encrypted files using the following names:

  • {original filename and extension}.grt

NOTES:

Decrypt.exe shows the following message:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.280.00

FIRST VSAPI PATTERN DATE:

16 Mar 2017

VSAPI OPR PATTERN File:

13.281.00

VSAPI OPR PATTERN Date:

17 Mar 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\Run
    • DecryptFiles = C:\Users\{username}\AppData\Local\Temp\decrypt.exe

Step 5

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.  
  • C:\Users\{username}\AppData\Local\Temp\id.txt
  • C:\Users\{username}\AppData\Local\Temp\adr.txt
  • C:\Users\{username}\AppData\Local\Temp\lnk.txt
  • C:\Users\{username}\AppData\Local\Temp\btc.txt
  • C:\Users\{username}\AppData\Local\Temp\del.bat
  • C:\Users\{username}\AppData\Local\Temp\decrypt.exe

Step 6

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