Analysis by: Jaime Benigno Reyes
ALIASES:

Trojan-Downloader.HTA.Agent.ef (Kaspersky)

 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: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan may be hosted on a website and run when a user accesses the said website.

  TECHNICAL DETAILS

File Size: 128,562 bytes
File Type: HTML, HTM
Memory Resident: Yes
Initial Samples Received Date: 05 May 2014

Arrival Details

This Trojan may be hosted on a website and run when a user accesses the said website.

Installation

This Trojan drops the following files:

  • %ProgramData%\padpd\2.dat (Windows Vista and higher versions)
  • %ProgramData%\padpd\d.bat (Windows Vista and higher versions)
  • %ProgramData%\padpd\resta.bat (Windows Vista and higher versions)
  • %ProgramData%\padpd\{userid}.bat (Windows Vista and higher versions)
  • %All Users Profile%\Application Data\padpd\2.dat (Versions lower than Windows Vista)
  • %All Users Profile%\Application Data\padpd\d.bat (Versions lower than Windows Vista)
  • %All Users Profile%\Application Data\padpd\resta.bat (Versions lower than Windows Vista)
  • %All Users Profile%\Application Data\padpd\{userid}.bat (Versions lower than Windows Vista)

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

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

  • %ProgramData%\padpd\{userid}.h (Windows Vista and higher versions)
  • %All Users Profile%\Application Data\padpd\{userid}.h (Versions lower than Windows Vista)

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

It creates the following folders:

  • %ProgramData%\padpd (Windows Vista and higher versions)
  • %All Users Profile%\Application Data\padpd (Versions lower than Windows Vista)

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
webpadpd = "%ProgramData%\padpd\{userid}" (Windows Vista and higher versions)

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
webpadpd = "%ProgramData%\padpd\{userid}" (Windows Vista and higher versions)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
webpadpd = "%All Users Profile%\Application Data\padpd\{userid}.h" (Versions lower than Windows Vista)

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
webpadpd = "%All Users Profile%\Application Data\padpd\{userid}.h" (Versions lower than Windows Vista)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Webpadpd
userid = "{userid}"

HKEY_CURRENT_USER\Software\Webpadpd
tmpdate = "{String value}"

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\Webpadpd

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://www.{BLOCKED}5.com/user/content_ajax_release5.php?{parameters}
  • http://{BLOCKED}a.us/user/h_check.php?uid={userid}
  • http://{BLOCKED}1a.us/user/h_info_ajax.php?checkuser={userid}

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.776.02
FIRST VSAPI PATTERN DATE: 05 May 2014
VSAPI OPR PATTERN File: 10.777.00
VSAPI OPR PATTERN Date: 06 May 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

Close all opened browser windows

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
    • webpadpd = "%ProgramData%\padpd\{userid}" (Windows Vista and higher versions)
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • webpadpd = "%All Users Profile%\Application Data\padpd\{userid}.h" (Versions lower than Windows Vista)
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • webpadpd = "%ProgramData%\padpd\{userid}" (Windows Vista and higher versions)
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • webpadpd = "%All Users Profile%\Application Data\padpd\{userid}.h" (Versions lower than Windows Vista)

Step 4

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software
    • Webpadpd

Step 5

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.
  • %ProgramData%\padpd (Windows Vista and higher versions)
  • %All Users Profile%\Application Data\padpd (Versions lower than Windows Vista)

Step 6

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