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RANSOM_CRYPDANGER.A

March 17, 2017
 Analysis by: Ryan Paolo Maglaque
 ALIASES:

Ransom:Win32/FileCryptor(Microsoft);W32/Filecoder.NJZ!tr(Fortinet);Win32/Filecoder.NJZ trojan(Eset-NOD32);

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


This Trojan 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:

111,843 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

09 Mar 2017

Payload:

Displays message/message boxes, Encrypts files

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %User Profile%\troll.txt - list of files from the directories
  • %System Root%\Users\Public\username.txt

(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.. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

It drops and executes the following files:

  • %User Profile%\myscript.vbs - ransom note

(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 Trojan renames encrypted files using the following names:

  • {Original File Name and Extension}.troll

It does the following:

  • Encrypts all files in the following directory:
    • %User Profile%\Desktop
    • %User Profile%\Downloads
    • %User Profile%\Documents
    • %User Profile%\Music
    • %User Profile%\Pictures
  • Displays the following ransom note:

NOTES:

The malware filename should contain the string DANGEROUS_RANSOM to execute.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.268.02

FIRST VSAPI PATTERN DATE:

10 Mar 2017

VSAPI OPR PATTERN File:

13.269.00

VSAPI OPR PATTERN Date:

11 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

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%\troll.txt
  • %System Root%\Users\Public\username.txt
  • %User Profile%\myscript.vbs

Step 4

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