BKDR_XPADO.DO

 Analysis by: Jaime Benigno Reyes

 ALIASES:

TrojanDownloader:Win32/Xpado.A (Microsoft), Trojan-Dropper.Win32.Sysn.qhq (Kaspersky), BackDoor-EKF.dr!5EDF4FC5577D (McAfee)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

26 Jul 2013

Arrival Details

This backdoor 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 backdoor drops the following component file(s):

  • %User Temp%\~df4e74.pdf
  • %User Temp%\kb71271.log - deleted afterwards
  • {Current Folder}\ka4281x3.log - deleted afterwards
  • %Application Data%\Location\WindowsUpdate.exe - also detected as BKDR_XPADO.DO

(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.. %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.)

It creates the following folders:

  • %Application Data%\Location

(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.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
WindowsUpdate = "%Application Data%\Location\WindowsUpdate.exe"

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Donwload and execute arbitrary file
  • Start a process, service and remote shell commands

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}.248.130/docs/index.jsp?/GAUV96.jsp?{encrypted stolen system information}

Information Theft

This backdoor gathers the following data:

  • Host name
  • IP number
  • Operating system
  • Time zone

NOTES:
This malware opens the dropped non-malicious .PDF file %User Temp%\~df4e74.pdf to trick user that it is a legitimate .PDF file.

The malware author can change the contents of index.jsp? in the malicious URL to point to another malicious URL. As of this writing, it is pointing to a non-malicious site.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.178.03

FIRST VSAPI PATTERN DATE:

26 Jul 2013

VSAPI OPR PATTERN File:

10.179.00

VSAPI OPR PATTERN Date:

27 Jul 2013

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

Identify and terminate files detected as BKDR_XPADO.DO

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • WindowsUpdate = "%Application Data%\Location\WindowsUpdate.exe"

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.
  • %User Temp%\~df4e74.pdf

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_XPADO.DO. 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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