Analysis by: Mark Joseph Manahan
ALIASES:

a variant of Win32/Plugax.A trojan (Eset)

 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:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

This backdoor may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 84,992 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 Feb 2013
Payload: Compromises system security, Collects system information

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_MDROP.REF
  • SWF_EXPLOIT.MC

Installation

This backdoor drops the following files:

  • %Application Data%\config.sys - configuration file

(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.)

It drops the following copies of itself into the affected system:

  • %Application Data%\googleupdate.exe

(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
Update = "%Application Data%\Googleupdate.exe"

Other System Modifications

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

HKEY_CURRENT_USER\Software\Classes
softbin = "{encrypted code}"

Backdoor Routine

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

  • Download and Load plugins - saved as %Temp%\{random}_p.ax or %Temp%\{username}.ax

(Note: %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)

It connects to the following websites to send and receive information:

  • {BLOCKED}.{BLOCKED}-job.com

Information Theft

This backdoor gathers the following data:

  • Computer Name
  • Admin rights
  • OS Version
  • Hostname

Other Details

This backdoor checks for the presence of the following process(es):

  • avp.exe
  • qqpctray.exe
  • 360tray.exe
  • kxetray.exe

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.714.03
FIRST VSAPI PATTERN DATE: 08 Feb 2013
VSAPI OPR PATTERN File: 9.715.00
VSAPI OPR PATTERN Date: 09 Feb 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

Remove the malware/grayware file dropped/downloaded by BKDR_PLUGAX.A

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
    • Update = "%Application Data%\Googleupdate.exe"
  • In HKEY_CURRENT_USER\Software\Classes
    • softbin = "{encrypted code}"

Step 5

Search and delete these files

[ Learn More ]
There may be some component 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.
  • %Application Data%\config.sys
  • %Temp%\{random}_p.ax
  • %Temp%\{username}.ax

Step 6

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