Analysis by: Alvin Bacani
ALIASES:

Exploit:Win32/CVE-2013-3906 (Microsoft); Trojan.Mdropper (Symantec)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This malware is involved in the targeted attacks that took advantage of an unpatched Microsoft Office vulnerability, namely CVE-2013-3906, on November 2013. Victims of this malware may find the security of their systems compromised.

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 takes advantage of software vulnerabilities in certain software to drop malicious files.

  TECHNICAL DETAILS

File Size: 370,287 bytes
File Type: DOCX
Initial Samples Received Date: 06 Nov 2013

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.

Dropping Routine

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

  • %TEMP%\a.l - damage file

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

Other Details

More information on this vulnerability can be found below:

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 10.394.05
FIRST VSAPI PATTERN DATE: 06 Nov 2013
VSAPI OPR PATTERN File: 10.395.00
VSAPI OPR PATTERN Date: 06 Nov 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

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%\a.l

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_ACTIFF.A. 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:

Download Fix-it Tool released by vendor to temporarily address the issue:


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