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RANSOM_XORBAT.A

May 13, 2016
 Analysis by: Rhena Inocencio
 ALIASES:

Trojan-Ransom.BAT.Agent.ay (Kaspersky)

 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:

Spammed via email


This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

BAT, EXE

Memory Resident:

No

Initial Samples Received Date:

25 Mar 2016

Payload:

Connects to URLs/IPs, Displays message/message boxes, Encrypts files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

This Trojan drops the following files:

  • %Desktop%\DECRYPT.txt - ransom note
  • %User Temp%\809133.txt - ransom note
  • %User Temp%\809133.cmd - uses 809133.exe to encrypt files. This is deleted after file encryption

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.. %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 System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.crypted
(Default) = "Crypted"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Crypted\shell\open\
command
(Default) = "notepad.exe %User Temp%\809133.txt"

Other Details

This Trojan encrypts files with the following extensions:

  • *.zip
  • *.rar
  • *.7z
  • *.tar
  • *.gz
  • *.xls
  • *.xlsx
  • *.doc
  • *.docx
  • *.pdf
  • *.rtf
  • *.ppt
  • *.pptx
  • *.sxi
  • *.odm
  • *.odt
  • *.mpp
  • *.ssh
  • *.pub
  • *.gpg
  • *.pgp
  • *.kdb
  • *.kdbx
  • *.als
  • *.aup
  • *.cpr
  • *.npr
  • *.cpp
  • *.bas
  • *.asm
  • *.cs
  • *.php
  • *.pas
  • *.vb
  • *.vcproj
  • *.vbproj
  • *.mdb
  • *.accdb
  • *.mdf
  • *.odb
  • *.wdb
  • *.csv
  • *.tsv
  • *.psd
  • *.eps
  • *.cdr
  • *.cpt
  • *.indd
  • *.dwg
  • *.max
  • *.skp
  • *.scad
  • *.cad
  • *.3ds
  • *.blend
  • *.lwo
  • *.lws
  • *.mb
  • *.slddrw
  • *.sldasm
  • *.sldprt
  • *.u3d
  • *.jpg
  • *.tiff
  • *.tif
  • *.raw
  • *.avi
  • *.mpg
  • *.mp4
  • *.m4v
  • *.mpeg
  • *.mpe
  • *.wmf
  • *.wmv
  • *.veg
  • *.vdi
  • *.vmdk
  • *.vhd
  • *.dsk

It does the following:

  • It accesses the following URLs to report infection status and to download component for encryption routine:
    • http://{domain}/counter/?ad=1DJSvvJhEaJvHfFxBiqoUdM4LPQQFs4iDJ&dc={value}
    • http://{domain}/counter/?id=rXf99xSu-CaXHM9gcc0cQ9m_ZAqPxVR6ffAJEPT3ntMUCmaFwrCfyZQGeh2b8fy-ZX23_9Am&rnd={random generated number}

      where {domain} can be any of the following:

      • {BLOCKED}ilen.com
      • {BLOCKED}r.ru
      • {BLOCKED}esearch.com
      • {BLOCKED}s.com.tr
      • www.{BLOCKED}n.ro

      • The downloaded file is saved as follows:
        • %User Temp%\809133.exe - component for file encryption. This is deleted after file encryption routine
      • It appends the extension .crypted to the encrypted files

      NOTES:

      This malware opens the dropped ransom note 809133.txt containing the following message:

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.426.07

FIRST VSAPI PATTERN DATE:

25 Mar 2016

VSAPI OPR PATTERN File:

12.427.00

VSAPI OPR PATTERN Date:

26 Mar 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

Delete this registry key

[ 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_LOCAL_MACHINE\SOFTWARE\Classes
    • .crypted

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_LOCAL_MACHINE\SOFTWARE\Classes\Crypted\shell\open\command
    • (Default) = "notepad.exe %User Temp%\809133.txt"

Step 5

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.
  • %Desktop%\DECRYPT.txt
  • %User Temp%\809133.txt
  • %User Temp%\809133.exe
  • %User Temp%\809133.cmd

Step 6

Scan your computer with your Trend Micro product to delete files detected as RANSOM_XORBAT.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 7

Restore encrypted files from backup.


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