WORM_SOHANAD.GZ
Windows 2000, Windows XP, Windows Server 2003

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
323,455 bytes
EXE
Yes
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
9.200
5.696.07
08 Dec 2008
5.697.00
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
Step 3
Delete this registry value
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 *""
- Window Title = "Ahsan Manan Khan Bhutta * Internet Explorer *""
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- Start_ShowRun = "0"
- Start_ShowRun = "0"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{208D2C60-3AEA-1069-A2D7-08002B30309D}
- (Default) = "Ahsan's Places"
- (Default) = "Ahsan's Places"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{20D04FE0-3AEA-1069-A2D8-08002B30309D}
- (Default) = "Ahsan's Computer"
- (Default) = "Ahsan's Computer"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{450D8FBA-AD25-11D0-98A8-0800361B1103}
- (Default) = "Ahsan's Document"
- (Default) = "Ahsan's Document"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{645FF040-5081-101B-9F08-00AA002F954E}
- (Default) = "G.W.Bush"
- (Default) = "G.W.Bush"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Runonce = "%Windows%\CSRSS.exe"
- Runonce = "%Windows%\CSRSS.exe"
- In HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\System
- DisableCMD = "1"
- DisableCMD = "1"
Step 4
Delete this registry key
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
- .au3
Step 5
Restore this modified registry value
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"
- From: (default) = "regfile"
- In HKEY_CLASSES_ROOT\.cmd
- From: (default) = "regfile"
To: (default) = "cmdfile"
- From: (default) = "regfile"
- In HKEY_CLASSES_ROOT\.com
- From: (default) = "regfile"
To: (default) = "comfile"
- From: (default) = "regfile"
- In HKEY_CLASSES_ROOT\.reg
- From: (default) = "exefile"
To: (default) = "regfile"
- From: (default) = "exefile"
- In HKEY_CLASSES_ROOT\.vbs
- From: (default) = "exefile"
To: (default) = "VBSFile"
- From: (default) = "exefile"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: HideFileExt = "1"
To: HideFileExt = "0"
- From: HideFileExt = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: SuperHidden = "0"
To: SuperHidden = "1"
- From: SuperHidden = "0"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: ShowSuperHidden = "0"
To: ShowSuperHidden = "1"
- From: ShowSuperHidden = "0"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
- From: CheckedValue = "0"
To: CheckedValue = "1"
- From: CheckedValue = "0"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = "explorer.exe, System.exe"
To: Shell = "Explorer.exe"
- From: Shell = "explorer.exe, System.exe"
Step 6
Reset the Internet Explorer Home and Search pages
Step 7
Search and delete AUTORUN.INF files created by WORM_SOHANAD.GZ that contain these strings
Step 8
Search and delete this file
- %Windows%\autorun.inf
Step 9
Search and delete this folder
- %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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