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Small.H

First posted on 13 September 2006.
Source: SecurityHome

Aliases :

Small.H is also known as Virus.Win32.Small.h.

Explanation :

Small.H is a virus with an internal spamming engine and backdoor functionality.

Small.H, originally named lsass.exe, spreads itself using an internal spaming-engine that is controlled through a previously set-up backdoor.

It fools the user into executing its exe file by using a Windows folder icon and file names such as:

Data.exe
Documents.exe
HotPictures.exe
HotXXX.exe
ImageGirls.exe
SexyBoy.exe
SexyGirls.exe
Songs.exe


Small.H creates several copies of itself:

C:[Documents and Settings][Current User]csrss.exe
C:[Documents and Settings][Current User]Local
SettingsTempFolderData.exe
C:[Documents and Settings][Current User]winlogon.exe
C:RECYCLERlsass.exe
C:RECYCLERmsinfomsinfo.exe


It creates a number of autostart keys in the registry such as:

[HKLMSOFTWAREMicrosoftWindows NTCurrentVersionWinlogon]

Added value to "System"
Added value to "Userinit"

[HKCUSoftwareMicrosoftWindows NTCurrentVersionWindows]

Added value to "load"

[HKCUSoftwareMicrosoftWindowsCurrentVersionPoliciesExplorerRun]

Added value to (Default)

Service key tree:

[HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMsInfo]

Solution :

Small.H duplicates file names and processes of legittimate Windows applications.

In order to determine the Small.H processes from the Windows processes, an enhanced Task Manager is needed. Process Explorer, freeware from Sysinternals, is one such application.

1. Download Process Explorer from Sysinternals website:
   http://www.sysinternals.com/Utilities/ProcessExplorer.html
   The application is a standalone exe file and does not require installation.
   


2. Run Process Explorer, in the process list find the following processes and end them by using the Kill option from the context menu (right-click).
   

   csrss.exe
lsass.exe
winlogon.exe


   
   
   The screenshot below shows the targets highlighted in purple. Note the use of the folder icons unlike the legititmate Windows files.
   
   
3. Remove the following files from the hard drive:
   

   C:\[Documents and Settings]\[Current User]\winlogon.exe
C:\[Documents and Settings]\[Current User]\csrss.exe
C:\[Documents and Settings]\[Current User]\Local Settings\Temp\FolderData.exe
C:\RECYCLER\lsass.exe
C:\RECYCLER\msinfo\msinfo.exe


   
   [Documents and Settings] is located on C:\Documents and Settings\ by default on most Windows XP systems and C:\Users\ on 2K/Vista.
   [Current User] folder name is same as currently logged in user name.
   


4. Download SmallH_RegCleaner.zip, then extract and merge "SmallH_RegCleaner.reg" into your registry by doubleclicking on the file.
   

Last update 13 September 2006

 

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