Threat Encyclopedia

PE_VIRLOCK.F-O

Publish date: March 21, 2015

ANALYSIS BY

Cris Nowell Pantanilla


PLATFORM:

Windows

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

  • Threat Type:File infector

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet, Infects files


This file infector arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

However, as of this writing, the said sites are inaccessible.

TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

16 Feb 2015

Payload:

Connects to URLs/IPs, Displays message/message boxes

Arrival Details

This file infector 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 file infector drops the following files:

  • %All Users%\[random characters]\[random characters]
  • %User Profile%\[random characters]\[random characters]
  • %User Temp%\file.vbs
  • %User Temp%\{random}.bat
  • %All Users%\{random}.txt - contains the list of all infected files for ransom

(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.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on 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.)

It drops and executes the following files:

  • %User Profile%\[random characters]\[random characters].exe - PE_VIRLOCK.F-O
  • %All Users%\[random characters]\[random characters].exe - PE_VIRLOCK.F-O

(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.)

It creates the following folders:

  • %All Users%\[random characters]
  • %User Profile%\[random characters]

(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 file infector adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
[random characters].exe = %User Profile%\[random characters]\[random characters].exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
[random characters].exe = %All User%\[random characters]\[random characters].exe

Other System Modifications

This file infector modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = 1

(Note: The default value data of the said registry entry is 0.)

File Infection

This file infector infects the following file types:

  • MS Office Files (.doc, .xls, .ppt, .mdb)
  • Adobe PDF Files (.pdf)
  • Archive Files(.zip, .rar)
  • Program Application Files (.exe)
  • Image Files (.gif, .png, .bmp, .jpg )
  • Media Files (.mp3, .wma)

Other Details

This file infector connects to the following URL(s) to check for an Internet connection:

  • google.com

It connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.45.170:9999
  • {BLOCKED}.{BLOCKED}.204.12:9999
  • {BLOCKED}.{BLOCKED}.164.69:9999

However, as of this writing, the said sites are inaccessible.

NOTES:

This malware retain the icons of the infected files.

The infected files are renamed to {file name}.{original file extension}.exe

Once the malware is installed, it will lock the screen and display the following image:

It commands the user to pay in order to unlock the infected computer.

SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.470.06

FIRST VSAPI PATTERN DATE:

10 Feb 2015

VSAPI OPR PATTERN File:

11.471.00

VSAPI OPR PATTERN Date:

10 Feb 2015

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

Restart in Safe Mode

[ Learn More ]

Step 3

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
    • [random characters].exe = "%User Profile%\[random characters]\[random characters].exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • [random characters].exe = "%All User%\[random characters]\[random characters].exe"

Step 4

Restore this modified 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\Explorer\Advanced
    • From: Hidden = 2
      To: Hidden = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = 1
      To: HideFileExt = 0

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
%All Users%\[random characters]
%User Profile%\[random characters]

Step 6

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 Temp%\file.vbs
%User Temp%\{random}.bat
%All Users%\[random characters]\[random characters]
%User Profile%\[random characters]\[random characters]

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as PE_VIRLOCK.F-O. 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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