Analysis by: Francis Xavier Antazo
ALIASES:

Ransom:Win32/Reveton.N (MICROSOFT), Trojan.Ransomlock.G (NORTON)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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 modifies the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size: 147,456 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 28 Jan 2015
Payload: Displays graphics/image, Collects system information

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 copies of itself into the affected system and executes them:

  • %System Root%\Documents and Settings\All Users\Application Data\{Random Characters}.dat

(Note: %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:

  • %System Root%\Documents and Settings\All Users\Application Data\{Random Characters}.js -- detected as JS_REVETON.SMN
  • %System Root%\Documents and Settings\All Users\Application Data\rundll32.exe (Normal File)

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

Autostart Technique

This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ctfmon.exe = "%System Root%\Documents and Settings\All Users\Application Data\rundll32.exe %System Root%\Documents and Settings\All Users\Application Data\{Random Characters}.dat, {Random}"

(Note: The default value data of the said registry entry is "%System%\ctfmon.exe".)

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\msconfig.lnk -- detected as LNK_REVETON.SM

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

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

  • {BLOCKED}.{BLOCKED}.217.85:80
  • {BLOCKED}.{BLOCKED}.217.85:443
  • {BLOCKED}.{BLOCKED}.215.165:80
  • {BLOCKED}.{BLOCKED}.215.165:443
  • {BLOCKED}.{BLOCKED}.53.102:80
  • {BLOCKED}.{BLOCKED}.53.102:443
  • {BLOCKED}.{BLOCKED}.53.197:80
  • {BLOCKED}.{BLOCKED}.53.197:443
  • {BLOCKED}.{BLOCKED}.236.194:443
  • {BLOCKED}.{BLOCKED}.236.194:80

NOTES:

It gathers the following information for its ransomware routine:

  • Malware Version and SubID
  • OS Version
  • System Default Language ID
  • System Metrics (Desktop Width and Height)
  • IP Address, Location and ISP

Using this information, it locks the screen (disabling taskmgr.exe) and displays a large window.

It downloads an encrypted file and save it to the infected system as:

  • %System Root%\Documents And Settings\All Users\Application Data\{reversed malware filename}.pad

  SOLUTION

Minimum Scan Engine: 9.700

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

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.
  • %System Root%\Documents and Settings\All Users\Application Data\{Random Characters}.dat
  • %System Root%\Documents and Settings\All Users\Application Data\{Random Characters}.js
  • %System Root%\Documents and Settings\All Users\Application Data\{Random Characters}.pad
  • %System Root%\Documents and Settings\All Users\Application Data\rundll32.exe

Step 5

Reset Internet security settings

[ Learn More ]

Step 6

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


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