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Threat Encyclopedia

TROJ_QHOST.FX


ALIASES:

Trojan:Win32/Qhost.EO, Trojan:Win32/Qhost.EO (Microsoft); Generic.gq (McAfee); Trojan.Gen (Symantec); Trojan.Win32.Qhost.xfr (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt)

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:

103,424 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Nov 2011

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.

Autostart Technique

This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
userinit = "%System%\userinit.exe,%User Profile%\Application Data\lsass.exe"

(Note: The default value data of the said registry entry is %System%\userinit.exe,.)

This report is generated via an automated analysis system.

SOLUTION

Minimum Scan Engine:

9.200

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

Identify and delete files detected as TROJ_QHOST.FX using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

Restore this modified 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\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: userinit="%System%\userinit.exe,%User Profile%\Application Data\lsass.exe"
      To: userinit=%System%\userinit.exe,

Step 4

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