Analysis by: Marfel Tiamzon
ALIASES:

TrojanDropper:Win32/Microjoin.gen!C (Microsoft); Trojan-Dropper.Win32.Microjoin.gen (Kaspersky); Artemis!1B7759FE55F5 (McAfee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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 executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 1,651,979 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 12 Oct 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.

Installation

This Trojan drops the following files:

  • %Program Files%\Adobe\Reader.exe - detected as TROJ_DROPPED.CU
  • %User Startup%\IEXPLORE.EXE - detected as TROJ_DROPPED.CU
  • %User Temp%\outlook.exe - detected as TROJ_DROPPED.CU

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %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.)

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

  • {malware path}\{random file name}.exe

Dropping Routine

This Trojan executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.490.03
FIRST VSAPI PATTERN DATE: 12 Oct 2011
VSAPI OPR PATTERN File: 8.491.00
VSAPI OPR PATTERN Date: 12 Oct 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_DROPPER.SPE

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPER.SPE. 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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