WORM_SOHANAD.GZ


 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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 modifies the user's Internet Explorer home page into a certain website. This action allows the malware to point to a website which may contain malware, putting the affected computer at greater risk of malware infection.

  TECHNICAL DETAILS

File Size:

323,455 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Dec 2008

Arrival Details

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops the following files:

  • %Windows%\autorun.inf

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

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

  • %System Root%\CSRSS.exe
  • %System Root%\Home Video.avi.exe
  • %Windows%\System.exe
  • %Windows%\Home Video.exe
  • %Start Menu%\Programs\Startup\winlogon.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %Start Menu% is the current user's Start Menu folder, which is usually C:\Windows\Profiles\{user name}\Start Menu on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu on Windows NT and C:\Windows\Start Menu or C:\Documents and Settings\{User name}\Start Menu on Windows 2000, XP, and Server 2003.)

It creates the following folders:

  • %System Root%\log

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

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
Runonce = "%Windows%\CSRSS.exe"

It modifies the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "explorer.exe, System.exe"

(Note: The default value data of the said registry entry is "Explorer.exe".)

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Window Title = "Ahsan Manan Khan Bhutta * Internet Explorer *"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Start_ShowRun = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CLSID\{208D2C60-3AEA-1069-A2D7-08002B30309D}
(Default) = "Ahsan's Places"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CLSID\{20D04FE0-3AEA-1069-A2D8-08002B30309D}
(Default) = "Ahsan's Computer"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CLSID\{450D8FBA-AD25-11D0-98A8-0800361B1103}
(Default) = "Ahsan's Document"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CLSID\{645FF040-5081-101B-9F08-00AA002F954E}
(Default) = "G.W.Bush"

HKEY_CURRENT_USER\Software\Policies\
Microsoft\Windows\System
DisableCMD = "1"

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

HKEY_CLASSES_ROOT\.bat (default)
"regfile" = "batfile"

HKEY_CLASSES_ROOT\.cmd
(default) = "regfile"

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

HKEY_CLASSES_ROOT\.com
(default) = "regfile"

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

HKEY_CLASSES_ROOT\.reg
(default) = "exefile"

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

HKEY_CLASSES_ROOT\.vbs
(default) = "exefile"

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

It adds the following registry keys as part of its installation routine:

HKEY_CLASSES_ROOT\.au3

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"

(Note: The default value data of the said registry entry is 0.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
SuperHidden = "0"

(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:

  • CSRSS.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 = CSRSS.exe
shell\Open\Command=CSRSS.exe
shell\Open\Default=1
shell\Explore\Command=CSRSS.exe
shell\Autoplay\Command=CSRSS.exe

Web Browser Home Page and Search Page Modification

This worm modifies the user's Internet Explorer home page to the following websites:

  • http://{BLOCKED}k.110mb.com/

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

5.696.07

FIRST VSAPI PATTERN DATE:

08 Dec 2008

VSAPI OPR PATTERN File:

5.697.00

VSAPI OPR PATTERN Date:

09 Dec 2008

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

Identify and delete files detected as WORM_SOHANAD.GZ using the Recovery Console

[ 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\Internet Explorer\Main
    • Window Title = "Ahsan Manan Khan Bhutta * Internet Explorer *""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • Start_ShowRun = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{208D2C60-3AEA-1069-A2D7-08002B30309D}
    • (Default) = "Ahsan's Places"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{20D04FE0-3AEA-1069-A2D8-08002B30309D}
    • (Default) = "Ahsan's Computer"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{450D8FBA-AD25-11D0-98A8-0800361B1103}
    • (Default) = "Ahsan's Document"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{645FF040-5081-101B-9F08-00AA002F954E}
    • (Default) = "G.W.Bush"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Runonce = "%Windows%\CSRSS.exe"
  • In HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\System
    • DisableCMD = "1"

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CLASSES_ROOT
    • .au3

Step 5

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\.bat
    • From: (default) = "regfile"
      To: (default) = "batfile"
  • In HKEY_CLASSES_ROOT\.cmd
    • From: (default) = "regfile"
      To: (default) = "cmdfile"
  • In HKEY_CLASSES_ROOT\.com
    • From: (default) = "regfile"
      To: (default) = "comfile"
  • In HKEY_CLASSES_ROOT\.reg
    • From: (default) = "exefile"
      To: (default) = "regfile"
  • In HKEY_CLASSES_ROOT\.vbs
    • From: (default) = "exefile"
      To: (default) = "VBSFile"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "1"
      To: HideFileExt = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: SuperHidden = "0"
      To: SuperHidden = "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"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "explorer.exe, System.exe"
      To: Shell = "Explorer.exe"

Step 6

Reset the Internet Explorer Home and Search pages

[ Learn More ]

Step 7

Search and delete AUTORUN.INF files created by WORM_SOHANAD.GZ that contain these strings

[ Learn More ]
[autorun]
open = CSRSS.exe
shell\Open\Command=CSRSS.exe
shell\Open\Default=1
shell\Explore\Command=CSRSS.exe
shell\Autoplay\Command=CSRSS.exe

Step 8

Search and delete this file

[ 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.
  • %Windows%\autorun.inf

Step 9

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.
  • %System Root%\log

Step 10

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