WORM_SOHANAD.OK

This worm arrives via removable drives. It 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 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.

Arrival Details

This worm arrives via removable drives.

It 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:

• %Desktop%\Search.lnk
• %Favorites%\Sioril.lnk
• %Start Menu%\Programs\Startup\Search bar.lnk
• %User Profile%\My Documents\Search bar.lnk
• %Windows%\Tasks\At1.job

(Note: %Desktop% is the current user's desktop, which is usually C:\Windows\Profiles\{user name}\Desktop on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Desktop on Windows NT, and C:\Documents and Settings\{User Name}\Desktop on Windows 2000, XP, and Server 2003.. %Favorites% is the current user's Favorites folder, which is usually C:\Windows\Favorites on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Favorites on Windows NT, and C:\Documents and Settings\{user name}\Favorites on Windows 2000, XP, and Server 2003.. %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.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %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%\chrome9.exe
• %Windows%\chrome9.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

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
Yahoo Messengger = "%System%\chrome9.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe chrome9.exe"

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

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Policies\
Microsoft\Internet Explorer

HKEY_CURRENT_USER\Software\Policies\
Microsoft\Internet Explorer\Control Panel

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Internet Explorer

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Internet Explorer\Control Panel

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
RunOnceComplete = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
RunOnceHasShown = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Search Assistant
DefaultSearchURL = "http://www.sioril.co.uk/index.php?page=search/web&search="

HKEY_CURRENT_USER\Software\Policies\
Microsoft\Internet Explorer\Control Panel
HomePage = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
RunOnceComplete = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
RunOnceHasShown = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Internet Explorer\Control Panel
HomePage = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
AtTaskMaxHours = "48"

Propagation

This worm searches for folders in all physical and removable drives then drops copies of itself inside the folder as {folder name}.EXE.

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

• {Drive Letter}:\chrome9.exe

Web Browser Home Page and Search Page Modification

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

• http://www.{BLOCKED}10.com/