Analysis by: Marfel Tiamzon
 PLATFORM:

Windows 98, ME, NT, 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives via removable drives.

It modifies registry entries to hide files with System and Read-only attributes.

It drops copies of itself in all removable and physical drives found in the system. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 170,861 bytes
File Type: EXE
Memory Resident: Yes

Arrival Details

This worm arrives via removable drives.

Installation

This worm drops the following files:

  • %User Temp%\i5g.dll
  • %system%\sool0.dll
  • %system%\ulso0.dll

(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.)

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

  • %system%\kvosoft.exe

Autostart Technique

This worm creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
kvasoft = %system%\kvosoft.exe

Other System Modifications

This worm modifies the following registry entries to hide files with System and Read-only attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 0

(Note: The default value data of the said registry entry is 1.)

Propagation

This worm drops copies of itself in all removable and physical drives found in the system.

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

  • cgoprig.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

;{garbage characters}
[AutoRun]
;{garbage characters}
open=cgoprig.exe
;{garbage characters}
shell\open\Command=cgoprig.exe
;{garbage characters}
shell\open\Default=1
;{garbage characters}
shell\explore\Command=cgoprig.exe
;{garbage characters}

Other Details

This worm deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 8.900

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

Restart in Safe Mode

[ Learn More ]

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_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Run
    • kvasoft = %system%\\kvosoft.exe

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_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced
    • From: Hidden=2
      To: Hidden=1
  • In HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced
    • From: ShowSuperHidden=0
      To: ShowSuperHidden=1
  • In HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced\\Folder\\Hidden\\SHOWALL
    • From: CheckedValue=0
      To: CheckedValue=1

Step 5

Search and delete these files

[ 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.

  • %System%\kvosoft.exe
  • cgoprig.exe
  • %User Temp%\i5g.dll
  • %System%\sool0.dll
  • %system%\ulso0.dll

Step 6

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


Did this description help? Tell us how we did.