Analysis by: Anthony Joe Melgarejo

ALIASES:

Exploit:Win32/CVE-2012-0158.CG (Microsoft), Trojan.Mdropper (Symantec), Exploit-MSExcel.ad (McAfee), Exp/20120158-A (Sophos), Exploit.Win32.CVE-2012 (Ikarus)

 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, Downloaded from the Internet

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.

  TECHNICAL DETAILS

File Size: 435,224 bytes
File Type: XLS
Memory Resident: No
Initial Samples Received Date: 23 Jan 2013
Payload: Drops files

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.

Installation

This Trojan drops and executes the following files:

  • %User Temp%\vmtools.exe - detected as BKDR_YART.A

(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.)

It drops the following non-malicious file:

  • %User Temp%\¥Ç©`¥¿¥µ¥ó¥×¥ë.xls

(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.)

Dropping Routine

This Trojan takes advantage of the following software vulnerabilities to drop malicious files:

Other Details

This Trojan opens the following files:

  • %User Temp%\¥Ç©`¥¿¥µ¥ó¥×¥ë.xls

(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:

When a machine is affected with this malware, MS Excel exits and runs again opening the non-malicious .XLS file to trick users into thinking that it is opening a normal .XLS file.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.676.02
FIRST VSAPI PATTERN DATE: 23 Jan 2013
VSAPI OPR PATTERN File: 9.677.00
VSAPI OPR PATTERN Date: 23 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_MDROPPR.NX

    • BKDR_YART.A

Step 3

Search and delete this file

[ Learn More ]
There may be some 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.
  • %User Temp\%¥Ç©`¥¿¥µ¥ó¥×¥ë.xls

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_MDROPPR.NX. 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.

Step 5

Download and apply these security patches Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.


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