Worm:Win32/Sohanad.Z

Worm:Win32/Sohanad.Z is a member of Win32/Sohanad - a family of worms that may spread via removable or network drives and particular messenger applications. It may also modify a number of system settings to facilitate its actions on an affected computer, and contact a remote host.

When executed, Worm:Win32/Sohanad.Z copies itself to the following locations:
%windir%\chrome.exe
<system folder>\chrome.exe

Note - <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32.

The malware modifies the following registry entry/ies to ensure that its copy executes at each Windows start:

Adds value: "Yahoo Messengger"
With data: "c:\windows\system32\chrome.exe"
To subkey: HKCU\SOFTWARE\Microsoft\windows\currentversion\run

Adds value: "Shell"
With data: "explorer.exe chrome.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

The malware creates the following file(s) on an affected machine:

The malware attempts to create a scheduled Windows task that runs the worm at 9:00 am every day of the week, by running the following Windows shell command instruction:
cmd.exe /C AT /delete /yes
cmd.exe /C AT 09:00 /interactive /EVERY:m,t,w,th,f,s,su <system folder>\chrome.exe

Variants of the Win32/Sohanad family may use a number of different methods in order to spread to other computers.
MSN Messenger
Win32/Sohanad may spread using a number of different messaging applications, including Yahoo Messenger, AIM, Windows Messenger and Google Talk. It sends a message to all of the infected user's contacts with a link to a copy of itself.

Network shares
Some variants of Win32/Sohanad also try to spread through network shares by querying the following registry entry and copying themselves to any shared folders specified by this entry: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares

Modifies system settings

Worm:Win32/Sohanad.Z modifies the affected computer system's settings by making the following changes to the registry:

Adds value: "DisableTaskMgr"
With data: "1"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System

This modification disables the system utility Task Manager.

Adds value: "NoFolderOptions"
With data: "1"
To subkey: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
This modification removes the Folder Options item from all Explorer menus and the Control Panel. Removing access to these options may hinder the affected user's ability to detect and remove the malware.

Contacts remote host

The malware may contact a remote host at h1.ripway.com using port 80. Commonly, malware may contact a remote host for the following purposes:

• To report a new infection to its author
• To receive configuration or other data
• To download and execute arbitrary files (including updates or additional malware)
• To receive instruction from a remote attacker
• To upload data taken from the affected computer

This malware description was produced and published using our automated analysis system's examination of file SHA1 c644a27fe0e7a6d895e16e41bd791b3749f95c22. If you would like to comment on this analysis, please send your feedback to mmpc-amd@microsoft.com.