PE_VIRUT.R-O

 Analysis by: jasperm

 ALIASES:

W32.SillyFDC (Symantec); W32/Autorun.worm.h (McAfee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: File infector

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This file infector may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

27 Jan 2011

Arrival Details

This file infector may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This file infector drops the following copies of itself into the affected system:

  • %System Root%\smss.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

This file infector adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
ctfmon.exe
Debugger = %System Root%\smss.exe

Other System Modifications

This file infector adds the following registry entries as part of its installation routine:

HKEY_CLASSES_ROOT\exefile
NeverShowExt =

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
exefile
NeverShowExt =

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_CLASSES_ROOT\exefile
(Default) = File Folder

(Note: The default value data of the said registry entry is Application.)

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
exefile
(Default) = File Folder

(Note: The default value data of the said registry entry is Application.)

NOTES:
This is Trend Micro detection for worms detected as worm variants infected by PE_VIRUX.R. It drops copies of itself in all removable and mapped drives using names of folders found in the said drives. It then hides the folders found in the drives. Since this worm is infected by PE_VIRUX.R, it has also the capabilities of PE_VIRUX.R

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI OPR PATTERN File:

7.797.00

VSAPI OPR PATTERN Date:

28 Jan 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 PE_VIRUT.R-O

Step 3

Identify and terminate files detected as PE_VIRUT.R-O

[ Learn More ]
  1. 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.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • ctfmon.exe

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CLASSES_ROOT\exefile
    • NeverShowExt =
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • CheckedValue = 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile
    • NeverShowExt =

Step 6

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CLASSES_ROOT\exefile
    • From: (Default) = File Folder
      To: (Default) = Application
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile
    • From: (Default) = File Folder
      To: (Default) = Application

Step 7

Scan your computer with your Trend Micro product to delete files detected as PE_VIRUT.R-O. 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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