Analysis by: Christopher Daniel So
 Modified by: Erika Bianca Mendoza
ALIASES:

TrojanDownloader:Win32/Ponmocup.A (Microsoft); W32.Changeup!gen (Symantec); Swisyn.s (McAfee); Trojan.Win32.Swisyn.jyb (Kaspersky)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: Varies
File Type: PE
Memory Resident: No
Initial Samples Received Date: 02 Nov 2008
Payload: Drops files

Arrival Details

This Trojan 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 Trojan drops and executes the following files:

  • %Application Data%\Help\WINCHAT.EXE - detected by Trend Micro as BKDR_AGENT.IOM

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It creates the following folders:

  • %Application Data%\Help

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

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
WINCHAT = "%Application Data%\Help\WINCHAT.EXE"

Dropping Routine

This Trojan drops the following files:

  • %System Root%\Documents and Settings\{user name}xplore.exe

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

Download Routine

This Trojan connects to the following malicious URLs:

  • http://{BLOCKED}ut4.cn/update/utu.dat

As of this writing, the said sites are inaccessible.

HOSTS File Modification

This Trojan adds the following strings to the Windows HOSTS file:

  • 127.0.0.1 thepiratebay.org
  • 127.0.0.1 www.thepiratebay.org
  • 127.0.0.1 mininova.org
  • 127.0.0.1 www.mininova.org
  • 127.0.0.1 forum.mininova.org
  • 127.0.0.1 blog.mininova.org
  • 127.0.0.1 suprbay.org
  • 127.0.0.1 www.suprbay.org

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 7.844.04
FIRST VSAPI PATTERN DATE: 18 Feb 2011

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by TROJ_DLOADR.LT

    • BKDR_AGENT.IOM

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
    • WINCHAT = %Application Data%\Help\WINCHAT.EXE

Step 4

Remove these strings added by the malware/grayware/spyware in the HOSTS file

[ Learn More ]
    • 127.0.0.1 thepiratebay.org
    • 127.0.0.1 www.thepiratebay.org
    • 127.0.0.1 mininova.org
    • 127.0.0.1 www.mininova.org
    • 127.0.0.1 forum.mininova.org
    • 127.0.0.1 blog.mininova.org
    • 127.0.0.1 suprbay.org
    • 127.0.0.1 www.suprbay.org
"

Step 5

Search and delete this file

[ 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.
  • %System Root%\Documents and Settings\{user name}xplore.exe

Step 6

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