Analysis by: Christopher Daniel So
ALIASES:

Trojan:Win32/Qhosts.AS (Microsoft), Trojan.Dropper (Symantec), QHost-Gen!bf (McAfee)

 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

Infection Channel: Dropped by other malware

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: Varies
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 22 Jun 2012
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.

Dropping Routine

This Trojan drops the following files:

  • %Windows%\{random file name}.torrent
  • %Windows%\26.scr - also detected by Trend Micro as TROJ_QHOST.BJF

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

NOTES:

It executes the dropped file %Windows%\26.scr and opens %Windows%\{random file name}.torrent.

The file %Windows%\26.scr drops the following files:

  • %Windows%\CONFIG.INI
  • %Windows%\CretClient.exe - detected by Trend Micro as HKTL_TERCLI
  • %Windows%\HDSetup.exe - detected by Trend Micro as TSPY_BANKER.SNP

It executes the dropped file %Windows%\HDSetup.exe. As a result, the malicious routines of the dropped file are exhibited on the affected system.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.210.04
FIRST VSAPI PATTERN DATE: 22 Jun 2012
VSAPI OPR PATTERN File: 9.211.00
VSAPI OPR PATTERN Date: 23 Jun 2012

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/grayware files dropped/downloaded by TROJ_QHOST.BJF

Step 3

Search and delete these files

[ 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.
  • %Windows%\{random file name}.torrent
  • %Windows%\CONFIG.INI

Step 4

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