ALIASES:

Tool:Win32/Hidekey.A (Microsoft); AdClicker-EV (McAfee); Trojan Horse (Symantec); Trojan-Downloader.Win32.Agent.ycj (Kaspersky); Trojan.Win32.ExplorerHijack (Sunbelt); Trojan.Crypt.CB (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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.

  TECHNICAL DETAILS

File Size: 8,704 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 27 Sep 2012

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 the following copies of itself into the affected system:

  • %Windows%\wisyst32.exe

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

Other System Modifications

This Trojan deletes the following files:

  • %User Temp%\ug.php

(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.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\7G21B2J74A

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\7G21B2J74A
7G21B2J74A = "4d4"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
7G21B2J74A = "%Windows%\wisyst32.exe"

Dropping Routine

This Trojan drops the following files:

  • %Windows%\logon.dll
  • %User Temp%\1.html
  • %User Temp%\1.html.$$$

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

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

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

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.

  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • 7G21B2J74A
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run

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_LOCAL_MACHINE\SOFTWARE\7G21B2J74A
    • 7G21B2J74A = "4d4"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • 7G21B2J74A = "%Windows%\wisyst32.exe"

Step 4

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %Windows%\logon.dll
  • %User Temp%\1.html
  • %User Temp%\1.html.$
$
  • In the Look In drop-down list, select My Computer then press Enter.
  • Once located, select the file then press SHIFT+DELETE to delete it.
  • Repeat the said steps for all files listed.

    • • For Windows Vista and Windows 7 users:

    1. Click Start>Computer.
    2. In the Search input box, type:
      • %Windows%\logon.dll
      • %User Temp%\1.html
      • %User Temp%\1.html.$
    3. Once located, select the file then press SHIFT+DELETE to delete it.
    4. Repeat the said steps for all files listed.
      *Note: Read the following Microsoft page if these steps do not work on Windows 7.

    Step 5

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

    Step 6

    Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

    • %User Temp%\ug.php


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