Analysis by: Byron Jon Gelera

ALIASES:

VBS/AutoRun.FS (ESET-NOD32); Worm:VBS/Gus.A (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Worm arrives via removable drives.

  TECHNICAL DETAILS

File Size: 5,737 bytes
File Type: VBS
Memory Resident: No
Initial Samples Received Date: 02 Mar 2013

Arrival Details

This Worm arrives via removable drives.

Installation

This Worm adds the following folders:

  • %Windows%\Psy
  • %Windows%\Spedssit

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops the following files:

  • {Drive Letter}:\autorun.inf (Hidden Attribute, used to execute a file named ini12.vbs)

It drops the following copies of itself into the affected system:

  • %Windows%\Psy\inyect12.vbs (Hidden Attribute)
  • %Windows%\Spedssit\inyect12.vbs (Hidden Attribute)

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Autostart Technique

This Worm drops the following files:

  • {Drive Letter}:\inyect.bat ← (Hidden Attribute, executes copy on the Drive Letter)

Other System Modifications

This Worm adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Sstem = "%Windows%\Psy\guy.vbs"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckValue = 0

(Note: The default value data of the said registry entry is {user defined}.)

Propagation

This Worm drops the following copy of itself in all physical and removable drives:

  • {Drive Letter}:\inyect12.vbs

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 9.764.05
FIRST VSAPI PATTERN DATE: 03 Mar 2013
VSAPI OPR PATTERN File: 9.765.00
VSAPI OPR PATTERN Date: 04 Mar 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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • Sstem = "%Windows%\Psy\guy.vbs"

Step 4

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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckValue = 0
      To: CheckValue = {user defined}

Step 5

Search and delete this folder

[ 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%\Psy
  • %Windows%\Spedssit

Step 6

Search and delete these files

[ 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.
  • {Drive Letter}:\inyect.bat
  • {Drive Letter}:\autorun.inf

Step 7

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


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