Analysis by: Mark Joseph Manahan
ALIASES:

JS/Kryptik.ACD trojan (Eset), Trojan-Dropper.JS.Adultush.k (Kasperksy), Trojan-Downloader.HTA.Agent.ce (v) (Sunbelt)

 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: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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: Varies
File Type: HTA, HTML, HTM
Memory Resident: Yes
Initial Samples Received Date: 24 Aug 2011

Arrival Details

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

Installation

This Trojan adds the following folders:

  • {All User's Profile\Application Data\csdat
  • %System Root%\Program Data\csdat

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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

  • {All User's Profile}\Application Data\csdat\5AXX73M5.hta
  • %System Root%\Program Data\csdat\5AXX73M5.hta

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It adds the following possibly malicious files or file components:

  • {All User's Profile\Application Data\csdat\d.bat
  • %System Root%\Program Data\csdat\d.bat

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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
webcsdat = "mshta {All User's Profile}\Application Data\csdat\5AXX73M5.hta"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
webcsdat = "mshta %System Root%\Program Data\csdat\5AXX73M5.hta"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
webcsdat = "mshta %System Root%\Program Data\csdat\5AXX73M5.hta"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
webcsdat = "mshta {All User's Profile}\Application Data\csdat\5AXX73M5.hta"

Other System Modifications

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

HKEY_CURRENT_USER\Software\Webcsdat\
userid

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://www.{BLOCKED}m.com/login.php?mode=login&type=force^userid={userid}
  • http://{BLOCKED}ges.com/user/h_check.php
  • http://{BLOCKED}ges.com/user/h_info_ajax.php

  SOLUTION

Minimum Scan Engine: 9.300
VSAPI OPR PATTERN File: 8.375.00
VSAPI OPR PATTERN Date: 25 Aug 2011

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 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\Webcsdat
    • userid

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
    • webcsdat = "mshta {All User's Profile}\Application Data\csdat\5AXX73M5.hta"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • webcsdat = "mshta %System Root%\Program Data\csdat\5AXX73M5.hta"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • webcsdat = "mshta %System Root%\Program Data\csdat\5AXX73M5.hta"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • webcsdat = "mshta {All User's Profile}\Application Data\csdat\5AXX73M5.hta"

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.
  • {All User's Profile\Application Data\csdat
  • %System Root%\Program Data\csdat

Step 6

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