Analysis by: Jasen Sumalapao
ALIASES:

Trojan-Dropper.Win32.Dorifel.gus (Kaspersky), Mal/Behav-112 (Sophos), Trojan.Win32.Generic.pak!cobra (Sunbelt), W32/Dorifel.GUS!tr (Fortinet)

 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: Spammed via email

This Trojan arrives as an attachment in a spammed email that uses Tibet and the 2012 Olympics as lure.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be manually installed by a user.

It uses common file icons to trick a user into thinking that the files are legitimate.

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

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 196,608 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 06 Aug 2012
Payload: Drops files, Displays images

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

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

It may be manually installed by a user.

Installation

This Trojan drops the following component file(s):

  • %System%\systimer.exe - detected as TROJ_RUGENT.A

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It uses common file icons to trick a user into thinking that the files are legitimate.

Dropping Routine

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

Other Details

This Trojan displays the following images:

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.308.01
FIRST VSAPI PATTERN DATE: 06 Aug 2012
VSAPI OPR PATTERN File: 9.309.00
VSAPI OPR PATTERN Date: 08 Aug 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_DROPPER.WSD

Step 3

Scan your computer with your Trend Micro product and note files detected as TROJ_DROPPER.WSD

Step 4

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.
  • {Malware Path}\Poster.jpg
  • {Malware Path}\Tibet and Olympics.jpg

Step 5

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