Spyware.CWSAddClass

SUMMARY

Behavior

Spyware.CWSAddClass is an Internet Explorer search function hijacker. It changes the search settings to a new search engine and adds a prefix to all the Web pages, so that typed Web addresses are channeled through an intermediary "enhanced-http site," which captures Internet-surfing information.

Symptoms

One or more files is detected as Spyware.CWSAddClass.

Transmission

Spyware.CWSAddClass is typically installed silently through an ActiveX installer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 29, 2004
• Virus Definitions (Intelligent Updater) September 25, 2004

TECHNICAL DETAILS

When Spyware.CWSAddClass is executed, it does the following:

1. Terminates the process, %System%Mshta.exe.
   
   Note: %System% is a variable that refers to the System folder. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
   
2. Creates the file, %Windir%Addclass.exe.
   
   Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows or C:Winnt.
   
   
3. Modifies the values:
   
   "SearchAssistant"="http:/ /ie.search.msn.com/{SUB_RFC1766}/srchasst/srchasst.htm"
   "CustomizeSearch"="http:/ /ie.search.msn.com/{SUB_RFC1766}/srchasst/srchcust.htm"
   "(Default)"="(value not set)"
   
   in the registry keys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerSearch
   HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerSearch
   
   to:
   
   "SearchAssistant"="http:/ /www.hand-book.com/search"
   "CustomizeSearch"="http:/ /www.hand-book.com/search"
   "(Default)"="http:/ /www.hand-book.com/search"
   
   
4. Modifies the values:
   
   "Search Page"="http:/ /www.microsoft.com/isapi/redir.dll?prd=ie&r=iesearch"
   "Default_Search_URL"="http:/ /www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch"
   "Start Page"="http:/ /www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home"
   
   in the registry keys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerMain
   HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerMain
   
   to:
   
   "Search Page"="http:/ /www.hand-book.com/search"
   "Default_Search_URL"="http:/ /www.hand-book.com/search"
   "Start Page"="http:/ /www.hand-book.com/hp"
   
   
5. Modifies the value:
   
   "(Default)"="(value not set)"
   
   in the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionURLPrefixes
   
   to:
   
   "(Default)"="http:/ /ehttp.cc/?"
   
   
6. Modifies the value:
   
   "(Default)"="http://"
   
   in the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionURLDefault Prefix
   
   to:
   
   "(Default)"="http:/ /ehttp.cc/?"
   
   
7. Adds the value:
   
   "Search Bar"="http:/ /www.hand-book.com/search"
   
   to the registry keys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerMain
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerMain
   
   
8. Adds the value:
   
   "(Default)"="http:/ /www.hand-book.com/search"
   
   to the registry key:
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerSearch URL
   
   
9. Adds the value:
   
   "AddClass"="%Windir%addclass.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the Spyware runs when you start Windows.

REMOVAL

The following instructions pertain to all Symantec antivirus products that support Security Risk detection.

1. Update the definitions.
2. Run a full system scan.
3. Reverse the changes that were made to the registry.
   

For specific details on each of these steps, read the following instructions.

1. To update the definitions
To obtain the most recent definitions, start your Symantec program and run LiveUpdate.

2. To run the scan

1. Start your Symantec antivirus program, and then run a full system scan.
   
2. If any files are detected as Spyware.CWSAddClass and depending on which software version you are using, you may see one or more of the following options:
   
   Note: This applies only to versions of Norton AntiVirus that support Security Risk detection. If you are running a version of Symantec AntiVirus Corporate Edition that supports Security Risk detection, and Security Risk detection has been enabled, you will only see a message box that gives the results of the scan. If you have questions in this situation, contact your network administrator.
   
   • Exclude (Not recommended): If you click this button, it will set the threat so that it is no longer detectable. That is, the antivirus program will keep the security risk on your computer and will no longer detect it to remove from your computer.
     
     
   • Ignore or Skip: This option tells the scanner to ignore the threat for this scan only. It will be detected again the next time that you run a scan.
     
     
   • Cancel: This option is new to Norton Antivirus 2005. It is used when Norton Antivirus 2005 has determined that it cannot delete a security risk. This Cancel option tells the scanner to ignore the threat for this scan only, and thus, the threat will be detected again the next time that you run a scan.
     
     To actually delete the security risk:
     • Click its file name (under the Filename column).
     • In the Item Information box that displays, write down the full path and file name.
     • Then use Windows Explorer to locate and delete the file.
       
       If Windows reports that it cannot delete the file, this indicates that the file is in use. In this situation, complete the rest of the instructions on this page, restart the computer in Safe mode, and then delete the file using Windows Explorer.
       
       
   • Delete: This option will attempt to delete the detected files. In some cases, the scanner will not be able to do this.
     • If you see a message, "Delete Failed" (or similar message), manually delete the file.
     • Click the file name of the threat that is under the Filename column.
     • In the Item Information box that displays, write down the full path and file name.
     • Then use Windows Explorer to locate and delete the file.
       
       If Windows reports that it cannot delete the file, this indicates that the file is in use. In this situation, complete the rest of the instructions on this page, restart the computer in Safe mode, and then delete the file using Windows Explorer.

3. Reverse the changes that were made to the registry

Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start > Run.
2. Type regedit
   
   Then click OK.
   
   
3. Navigate to and delete the following values in their respective keys:
   
   key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerMain
   value: "Search Bar"="http:/ /www.hand-book.com/search"
   
   key: HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerMain
   value: "Search Bar"="http:/ /www.hand-book.com/search"
   
   key: HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerSearchURL
   value: "(Default)"="http:/ /www.hand-book.com/search"
   
   key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   value: "AddClass"="%Windir%addclass.exe"
   
   key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionURLPrefixes
   value: "(Default)"=""
   
   key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerSearch
   value: "(Default)"=""
   
   
4. Change the values in the keys below to the new value:
   
   key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionURLDefault Prefix
   value: "(Default)"="http://"

key: HKEY_CURRENT_USERSOFTWAREMicrosoftInternet ExplorerMain
values: "Search Page"="http://www.microsoft.com/isapi/redir.dll?prd=ie&r=iesearch"
"Default_Search_URL"="http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch"
"Start Page"="http://www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home"

key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerMain
values: "Search Page"="http://www.microsoft.com/isapi/redir.dll?prd=ie&r=iesearch"
"Default_Search_URL"="http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch"
"Start Page"="http://www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home"

key: HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerSearch
values: "SearchAssistant"="http://ie.search.msn.com/{SUB_RFC1766}/srchasst/srchasst.htm"
"CustomizeSearch"="http://ie.search.msn.com/{SUB_RFC1766}/srchasst/srchcust.htm"