Analysis by: Kathleen Notario
 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 attempts to exploit the "Excel Integer Overrun Vulnerability" (CVE-2011-0097) in certain versions of Microsoft Excel.

This Trojan contains a malicious file embedded in its code.

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

It does not have any propagation routine.

It does not have any backdoor routine.

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

It does not have any downloading capability.

It does not have any information-stealing capability.

  TECHNICAL DETAILS

File Size: 110,592 bytes
File Type: XLS
Initial Samples Received Date: 19 Dec 2011
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%\svchost.exe – detected as TROJ_DLOADR.BFK

(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.)

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Dropping Routine

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

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

Download Routine

This Trojan does not have any downloading capability.

Information Theft

This Trojan does not have any information-stealing capability.

NOTES:

It attempts to exploit the "Excel Integer Overrun Vulnerability" (CVE-2011-0097) in the following versions of Microsoft Excel:

  • Microsoft Excel 2002 Service Pack 3
  • Microsoft Excel 2003 Service Pack 3
  • Microsoft Excel 2007 Service Pack 2
  • Microsoft Excel 2010
  • Office 2004 for Mac
  • Office 2008 for Mac
  • Open XML File Format Converter for Mac
  • Excel Viewer Service Pack 2
  • Office Compatibility Pack for Word, Excel and Powerpoint 2007 File Formats Service Pack 2

It also attempts to hide its malicious routines from the user by dropping and opening a non-malicious .XLS file, %User Temp%\{characters}.xls.

It does not have rootkit capabilities.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.654.02
FIRST VSAPI PATTERN DATE: 19 Dec 2011
VSAPI OPR PATTERN File: 8.655.00
VSAPI OPR PATTERN Date: 20 Dec 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_MDROPPR.BF

     
    • TROJ_DLOADR.BFK

Step 3

Search and delete this file

[ 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.
  • %User Temp%\{characters}.xls

Step 4

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

NOTES:

For updates on available workarounds and patches for this vulnerability, please refer to the following page:


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