Threat Encyclopedia

BAT_CRYPVAULT.A

Publish date: April 06, 2015

ANALYSIS BY

Rommel Abraham Joven


ALIASES:

Trojan-Ransom.BAT.Scatter.al(Kaspersky); Ransom:BAT/Xibow.H(Microsoft); Trojan.Ransomcrypt.R(Symantec)

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


This crypto-ransomware encrypts files and appends an extension that may look like it is a quarantined file. Quarantined files are usually done by anti-malware products.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

This Trojan may arrive bundled with malware packages as a malware component. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes itself after execution.

TECHNICAL DETAILS

File Size:

Varies

Memory Resident:

No

Initial Samples Received Date:

24 Mar 2015

Payload:

Connects to URLs/IPs, Steals information, Encrypts files, Displays message/message boxes, Displays graphics/image

Arrival Details

This Trojan may arrive bundled with malware packages as a malware component.

It 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 Temp%\VAULT.txt
  • %User Temp%\VAULT.hta
  • %appdata%\VAULT.hta
  • %User Temp%\a.qq
  • %User Temp%\gk.vlt
  • %User Temp%\pk.vlt
  • %User Temp%\vaultkey.vlt
  • %User Temp%\cryptlist.lst
  • %User Temp%\conf.list
  • %User Temp%\confclean.list
  • %User Temp%\cryptlist.cmd
  • %User Temp%\up.vbs
  • %User Temp%\ultra.js

(Note: %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.)

Autostart Technique

This Trojan creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
TNotification = "notepad %User Temp%\VAULT.txt"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
VAULT Notification = "mshta %appdata%\VAULT.hta"

File Infection

This Trojan avoids infecting files that contain the following strings in their names:

  • windows
  • temp
  • recycle
  • program
  • appdata
  • avatar
  • roaming
  • msoffice
  • temporary
  • sample
  • themes
  • uploads
  • csize
  • resource
  • internet
  • com_
  • intel
  • common
  • resources
  • texture
  • profiles
  • library
  • clipart
  • manual
  • games
  • framework64
  • setupcache
  • autograph
  • maps
  • amd64
  • cache
  • support
  • guide
  • abbyy
  • application
  • thumbnails
  • avatars
  • template
  • adobe

Download Routine

This Trojan connects to the following URL(s) to download its component file(s):

  • http://{BLOCKED}lpknfp.onion.city

It saves the files it downloads using the following names:

  • %User Temp%\enigma.exe

(Note: %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.)

Other Details

This Trojan encrypts files with the following extensions:

  • *.xls
  • *.doc
  • *.pdf
  • *.rtf
  • *.psd
  • *.dwg
  • *.cdr
  • *.cd
  • *.mbd
  • *.1cd
  • *.dbf
  • *.sqlite
  • *.jpg
  • *.zip
  • *.7z

It renames encrypted files using the following names:

  • {file name and extension}.vault

It deletes itself after execution.

NOTES:

This malware recovers the following information from browsers installed on the affected system:

  • Password
  • User name
  • Website

It requires the following files as its components for infection:

  • %User Temp%\301.vlt
  • %User Temp%\logs.vlt
  • %User Temp%\temp.vlt

It then renames and executes them as part of its routine:

  • %User Temp%\301.vlt renamed to audiodg.exe
  • %User Temp%\logs.vlt renamed to svchost.exe
  • %User Temp%\temp.vlt renamed to tick.exe

When the required components exist, it drops the following files:

  • %appdata%\CONFIRMATION.KEY
  • %appdata%\VAULT.KEY
  • %User Temp%\ch.vlt
  • %User Temp%\CONFIRMATION.KEY
  • %User Temp%\cookie.vlt
  • %User Temp%\random_seed
  • %User Temp%\secring.gpg
  • %User Temp%\trustdb.gpg
  • %User Temp%\VAULT.KEY
  • %User Temp%\VAULT2.KEY
  • %User Temp%\win.vbs
  • %userprofile%\Desktop\VAULT-README.txt
  • %userprofile%\Desktop\VAULT.KEY

It encrypts file from drives B to Z. It deletes components used in encryption.

It changes the icons of encrypted files:

It opens a window with instructions to restore files whenever an encrypted file is accessed:

It displays it's ransom note %User temp%\VAULT.txt every system start up:

It displays it's ransom image %appdata%\VAULT.hta every system start up:

SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.560.01

FIRST VSAPI PATTERN DATE:

24 Mar 2015

VSAPI OPR PATTERN File:

11.561.00

VSAPI OPR PATTERN Date:

25 Mar 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

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
    • TNotification="notepad %User Temp%\VAULT.txt"
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • VAULT Notification="mshta %appdata%\VAULT.hta"

Step 5

Search and delete these files

[ 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%\VAULT.txt
  • %User Temp%\VAULT.hta
  • %User Temp%\a.qq
  • %User Temp%\gk.vlt
  • %User Temp%\pk.vlt
  • %User Temp%\vaultkey.vlt
  • %User Temp%\cryptlist.lst
  • %User Temp%\conf.list
  • %User Temp%\confclean.list
  • %User Temp%\cryptlist.cmd
  • %User Temp%\up.vbs
  • %User Temp%\ultra.js
  • %User Temp%\enigma.exe
  • %User Temp%\audiodg.exe
  • %User Temp%\svchost.exe
  • %User Temp%\tick.exe
  • %User Temp%\ch.vlt
  • %User Temp%\win.vbs
  • %User Temp%\cookie.vlt
  • %User Temp%\VAULT.KEY
  • %User Temp%\secring.gpg
  • %User Temp%\trustdb.gpg
  • %User Temp%\random_seed
  • %User Temp%\CONFIRMATION.KEY
  • %User Temp%\VAULT2.KEY
  • %appdata%\VAULT.hta
  • %appdata%\CONFIRMATION.KEY
  • %appdata%\VAULT.KEY
  • %userprofile%\Desktop\VAULT.KEY
  • %userprofile%\Desktop\VAULT-README.txt

Step 6

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


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