Analysis by: Anthony Joe Melgarejo
ALIASES:

Trojan:Win32/Zawat.A (Microsoft), W32/Scar.HDAS!tr (Fortinet)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Spammed via email

This malware arrives via spammed email message written in Japanese language that bore the subject, New Year Greetings.

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

  TECHNICAL DETAILS

File Size: 1,602,760 bytes
File Type: EXE
File Compression: UPX
Memory Resident: No
Initial Samples Received Date: 08 Jan 2013
Payload: Drops files

Arrival Details

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

Installation

This Trojan drops the following files:

  • %User Temp%\acrotray.exe - detected as TROJ_FAKEMS.CA

(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.)

NOTES:

Below is the screenshot of the spammed message:

It acts as a file archive manager with password lock capability to trick users from suspecting its real malicious intent.

It drops the following image file when the correct password is entered:

  • 11.jpg

%User Temp%\acrotray.exe does not require any passwords to be dropped. It is dropped immediately upon execution.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.650.01
FIRST VSAPI PATTERN DATE: 11 Jan 2013
VSAPI OPR PATTERN File: 9.651.00
VSAPI OPR PATTERN Date: 12 Jan 2013

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

Remove malware/grayware files dropped/downloaded by TROJ_DROPPER.AJM

    • TROJ_FAKEMS.CA

Step 3

Identify and terminate files detected as TROJ_DROPPER.AJM

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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