Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Copies itself in all available physical drives, Propagates via removable drives

This worm may be downloaded by other malware/grayware/spyware from remote sites. It may be unknowingly downloaded by a user while visiting malicious websites.

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

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: 164,864 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 01 Dec 2010
Payload: Downloads files

Arrival Details

This worm may be downloaded by other malware/grayware/spyware from remote sites.

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

Installation

This worm drops the following copies of itself into the affected system:

  • %User Temp%\rbking.exe

(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 component file(s):

  • %User Temp%\rbking0.dll - also detected as WORM_GAMETHI.CAY

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
king_rb = "%User Temp%\rbking.exe"

Other System Modifications

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

HKEY_CLASSES_ROOT\CLSID\MADOWN
urlinfo = "tfsxr.r"

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

  • skg1.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:

[AutoRun]
open=skg1.exe
shell\open\Command=skg1.exe

Download Routine

This worm downloads an updated copy of itself from the following website(s):

  • http://www.{BLOCKED}8.com/1rb/ar1.rar
  • http://www.{BLOCKED}8.com/1rb/ar.rar

Other Details

This worm deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 7.667.80
FIRST VSAPI PATTERN DATE: 01 Dec 2010

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
    • king_rb = %User Temp%\rbking.exe
  • In HKEY_CLASSES_ROOT\CLSID\MADOWN
    • urlinfo = tfsxr.r

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

Step 5

Search and delete AUTORUN.INF files created by WORM_GAMETHI.CAY that contain these strings

[ Learn More ]
[AutoRun]
open=skg1.exe
shell\open\Command=skg1.exe

Step 6

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