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BAT_CRYPTOR.A
Aliases: Trojan-Ransom.BAT.Agent.aa(Kaspersky)
Malware type: Trojan
Destructive: No
Platform: Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
Encrypted: No
In the wild: Yes

Overview


Infection Channel: Downloaded from the Internet, Dropped by other malware

This ransomware uses the GNU Privacy Guard application, a legitimate app in order to encrypt files.

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
File type: BAT
Memory resident: No
Initial samples received date: 17 Jul 2014
Payload: Encrypts files, Drops files

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 creates the following folders:

  • %User Temp%\KEYPRIVATE

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Dropping Routine

This Trojan drops the following files:

  • C:\PAYCRYPT_GMAIL_COM.txt
  • D:\PAYCRYPT_GMAIL_COM.txt
  • %Application Data%\Desktop\PAYCRYPT_GMAIL_COM.txt
  • %Desktop%\PAYCRYPT_GMAIL_COM.txt
  • %User Temp%\PAYCRYPT_GMAIL_COM.txt
  • %User Temp%\pycrp.bin -once this already existed it will not continue its routine

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.. %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\Desktop on Windows Vista and 7.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other Details

This Trojan encrypts files with the following extensions:

  • *.xls
  • *.xlsx
  • *.doc
  • *.docx
  • *.pdf
  • *.jpg
  • *.cd
  • *.jpeg
  • *.1cd
  • *.rar
  • *.mdb
  • *.zip

It renames encrypted files using the following names:

  • {file name and extension}.paycrypt@gmail_com

It deletes itself after execution.

NOTES:

It encrypts file from drives B:\ to Z:\.

The dropped file PAYCRYPT_GMAIL_COM.txt contains the following:

  • BLOCK DATE: {Date and time accomplished the encryption}

It deletes the following directory %APPDATA%\gnupg.

It will delete components used in encryption.

When the required components exist, it will dropped the following files:

  • %User Temp%\DECODE.zip
  • C:\DECODE.zip
  • D:\DECODE.zip
  • %User Profile%\Desktop\DECODE.zip
  • %Application Data%\Desktop\DECODE.zip
  • %User Temp%\KEY.PRIVATE
  • %User Temp%\KEYPRIVATE\KEY.PRIVATE
  • %Application Data%\KEY.PRIVATE
  • C:\KEY.PRIVATE
  • D:\KEY.PRIVATE
  • %Desktop%\KEY.PRIVATE
  • %Application Data%\Desktop\KEY.PRIVATE

Solution


Minimum scan engine: 9.700
First VSAPI Pattern File: 10.938.05
First VSAPI Pattern Release Date: 22 Jul 2014
VSAPI OPR Pattern Version: 10.939.00
VSAPI OPR Pattern Release Date: 23 Jul 2014

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

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.
  • C:\PAYCRYPT_GMAIL_COM.txt
  • D:\PAYCRYPT_GMAIL_COM.txt
  • %Application Data%\Desktop\PAYCRYPT_GMAIL_COM.txt
  • %Desktop%\PAYCRYPT_GMAIL_COM.txt
  • %User Temp%\PAYCRYPT_GMAIL_COM.txt
  • %User Temp%\pycrp.bin
  • %User Temp%\DECODE.zip
  • C:\DECODE.zip
  • D:\DECODE.zip
  • %User Profile%\Desktop\DECODE.zip
  • %Application Data%\Desktop\DECODE.zip
  • %User Temp%\KEY.PRIVATE
  • %Application Data%\KEY.PRIVATE
  • C:\KEY.PRIVATE
  • D:\KEY.PRIVATE
  • %Desktop%\KEY.PRIVATE
  • %Application Data%\Desktop\KEY.PRIVATE

Step 4

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.
 
  • %User Temp%\KEYPRIVATE

Step 5

Scan your computer with your Trend Micro product to delete files detected as BAT_CRYPTOR.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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Analysis By: Adrian Cofreros

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