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RANSOM_COMRADE.A

February 06, 2018
 Analysis by: Noel Anthony Llimos
 ALIASES:

Ransom.HiddenTear (Norton), HEUR:Trojan.Win32.Generic (Kaspersky), Ransom:Win32/HiddenTear.gen [generic] (Microsoft)

 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:

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 drops files as ransom note.

  TECHNICAL DETAILS

File Size:

6069760 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Oct 2017

Payload:

Connects to URLs/IPs, Encrypts files, Displays message/message boxes

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 copies of itself into the affected system:

  • %User Profile%\Documents\Windows.exe

(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.)

Autostart Technique

This Ransomware creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows_Defender = %User Profile%\Documents\Windows.exe

Other Details

This Ransomware connects to the following possibly malicious URL:

  • https://poop777.{BLOCKED}hostapp.com/scam.php?info=

It encrypts files with the following extensions:

  • .txt
  • .doc
  • .docx
  • .xls
  • .xlsx
  • .ppt
  • .pptx
  • .odt
  • .jpg
  • .png
  • .csv
  • .sql
  • .mdb
  • .sln
  • .php
  • .asp
  • .aspx
  • .html
  • .xml
  • .psd
  • .mp3
  • .mp4
  • .mov
  • .wav
  • .ogg
  • .ico
  • .tiff
  • .jpeg
  • .obj
  • .c
  • .h
  • .cs
  • .cpp
  • .ttf
  • .rtf

Ransomware Routine

This Ransomware appends the following extension to the file name of the encrypted files:

  • .comrade

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

  • %Desktop%\DECRYPT_FILES.txt

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.738.06

VSAPI OPR PATTERN File:

13.739.00

Step 1

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 2

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

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
    • Windows_Defender = %User Profile%\Documents\Windows.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.
  • %User Profile%\Documents\Windows.exe
  • %Desktop%\DECRYPT_FILES.txt

Step 6

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