Modified by: Mark Joseph Manahan
ALIASES:

Troj/Cosmu-O (Webroot) ,Troj/Cosmu-O (Sophos) ,W32/Cosmu.ANHF!tr (Fortinet) ,W32/VBTrojan.9!Maximus (Fprot) ,Trojan.Win32.Cosmu (Ikarus) ,Trojan:Win32/Msposer.E (Microsoft) ,Win32/VB.NAX virus (Eset) ,Trojan.Gen (Symantec) ,Trj/Sinowal.WWG (Panda) ,Trojan-Dropper.Win32.Msposer.e (v) (Sunbelt)

 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: File infector

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This file infector may arrive using one or multiple arrival methods.

  TECHNICAL DETAILS

File Size: Varies
File Type: EXE, DOC, DOCX
Memory Resident: Yes
Initial Samples Received Date: 05 Oct 2012
Payload: Drops files

Arrival Details

This file infector arrives via the following means:

  • Infected by PE_COSVAR.A-O

Installation

This file infector drops and executes the following files:

  • %Windows%\Temp\_$Cf\osk.exe - detected as PE_COSVAR.A-O

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

It drops the following non-malicious file:

  • %Windows%\Temp\_$Cf\{Malware Name}.{extension} - original document file
    where extension is either docx or doc

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

It creates the following folders:

  • %Windows%\Temp\_$Cf

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

File Infection

This is the Trend Micro detection for files infected by:

  • PE_COSVAR.A-O

NOTES:

The dropped PE_COSVAR.A-O performs the file infection. It infects the following files:

  • .doc
  • .docx

  SOLUTION

Minimum Scan Engine: 9.700
VSAPI OPR PATTERN File: 9.443.00
VSAPI OPR PATTERN Date: 05 Oct 2012

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 the malware/grayware file that dropped/downloaded PE_COSVAR.A

    • PE_COSVAR.A-O

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Windows%\Temp\_$Cf

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as PE_COSVAR.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:

Users may also visit the link provided below for the corresponding fixtool for this detection:


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