Analysis by: Ryan Gardo
ALIASES:

Riskware/Filecoder_Cryptorium (Fortinet)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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: 128,512 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 16 Dec 2016
Payload: Displays graphics/image, 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.

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "1"

Process Termination

This Trojan terminates the following processes if found running in the affected system's memory:

  • rundll32.exe

Other Details

This Trojan renames encrypted files using the following names:

  • {original filename}.ENC

It does the following:

  • Encrypts files in the following directories:
    • %User Profile%\Downloads
    • %User Profile%\Videos
    • %User Profile%\Pictures
    • %User Profile%\Music
    • %User Profile%\Desktop
    • %User Profile%\Documents
    • C:\ProgramData\Microsoft\Windows\Start Menu\Programs

(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.)

NOTES:

This ransomware shows the following image after encryption:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.964.03
FIRST VSAPI PATTERN DATE: 16 Dec 2016
VSAPI OPR PATTERN File: 12.965.00
VSAPI OPR PATTERN Date: 17 Dec 2016

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\Policies\System
    • DisableTaskMgr = "1"

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPTORIUM.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 6

Restore encrypted files from backup.


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