Analysis by: Julie Anne Cabuhat
ALIASES:

Ransom.Crystal (Malwarebytes), W32/Trojan.SW.gen!Eldorado (F-Prot)

 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.

It is capable of encrypting files in the affected system.

  TECHNICAL DETAILS

File Size: 73,164 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 28 Feb 2017
Payload: 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:

  • %Desktop%\UserFilesLocker.exe - contains ransom note, decryption instructions
  • %Desktop%\_encrypt.pinfo - contains information used by UserFilesLocker.exe (bitcoin amount, email address, ID)
  • %User Profile%\Documents\_encrypt.pinfo - contains information used by UserFilesLocker.exe (bitcoin amount, email address, ID)

(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.. %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 and executes the following files:

  • %User Profile%\Documents\UserFilesLocker.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.)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
IUDL = "%User Profile%\Documents\UserFilesLocker.exe "

Other Details

This Trojan renames encrypted files using the following names:

  • {Original filename and extension}.ENCR

It does the following:

  • It only encrypts the files in the subfolders if it encrypts a file in the current folder/location. It encrypts files in the following locations:
    • %Desktop%
    • %User Profile%\Document
    • %User Profile%\Music
    • %User Profile%\Videos
    • %User Profile%\Pictures
    • %User Profile%\Downloads
    • %All User Profile%\Pictures
    • %All User Profile%\Music
    • %All User Profile%\Videos
    • %All User Profile%\Documents
    • {Fixed hard drive letter}:\

It is capable of encrypting files in the affected system.

NOTES:

The ransomware displays a window containing multiple tabs containing information about the encryption algorithm used, payment, how to contact them, and data recovery.

Information about encryption algorithm used:

Information about payment:

Information about how to contact them:

Decryption/ Data recovery tab:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.252.02
FIRST VSAPI PATTERN DATE: 01 Mar 2017
VSAPI OPR PATTERN File: 13.253.00
VSAPI OPR PATTERN Date: 02 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
    • IUDL = "%User Profile%\Documents\UserFilesLocker.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.
  • %Desktop%\UserFilesLocker.exe
  • %User Profile%\Documents\UserFilesLocker.exe
  • %Desktop%\_encrypt.pinfo
  • %User Profile%\Documents\_encrypt.pinfo

Step 6

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