Spyware.CWSAddClass

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Updated: February 13, 2007 11:39:40 AM
Type: Spyware
Risk Impact: High
File Names: Addclass.exe
Systems Affected: Windows

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.

Antivirus Protection Dates

  • Initial Rapid Release version October 02, 2014 revision 022
  • Latest Rapid Release version February 01, 2015 revision 020
  • Initial Daily Certified version September 25, 2004
  • Latest Daily Certified version January 17, 2008 revision 033
  • Initial Weekly Certified release date September 29, 2004

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Updated: February 13, 2007 11:39:40 AM
Type: Spyware
Risk Impact: High
File Names: Addclass.exe
Systems Affected: Windows


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:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (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_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Search
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Search

    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_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main

    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_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\URL\Prefixes

    to:

    "(Default)"="http:/ /ehttp.cc/?"

  6. Modifies the value:

    "(Default)"="http://"

    in the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\URL\Default Prefix

    to:

    "(Default)"="http:/ /ehttp.cc/?"

  7. Adds the value:

    "Search Bar"="http:/ /www.hand-book.com/search"

    to the registry keys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main

  8. Adds the value:

    "(Default)"="http:/ /www.hand-book.com/search"

    to the registry key:

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Search URL

  9. Adds the value:

    "AddClass"="%Windir%\addclass.exe"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the Spyware runs when you start Windows.


Updated: February 13, 2007 11:39:40 AM
Type: Spyware
Risk Impact: High
File Names: Addclass.exe
Systems Affected: Windows


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_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    value: "Search Bar"="http:/ /www.hand-book.com/search"

    key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main
    value: "Search Bar"="http:/ /www.hand-book.com/search"

    key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\SearchURL
    value: "(Default)"="http:/ /www.hand-book.com/search"

    key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    value: "AddClass"="%Windir%\addclass.exe"

    key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\URL\Prefixes
    value: "(Default)"=""

    key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Search
    value: "(Default)"=""

  4. Change the values in the keys below to the new value:

    key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\URL\Default Prefix
    value: "(Default)"="http://"