INTERNET EXPLORER ADD-ON MANAGEMENT

(Windows XP Service Pack 2)


Windows XP SP2 contains many security enhancements and feature additions. One of the important feature addition in Internet Explorer is Manage Add-ons. This is a great feature of Internet Explorer, which was implemented by the developers after reviewing the Windows Error Reporting logs. It has been noted that third-party add-ons contribute to the majority of Internet Explorer crashes. This is very true as we are seeing a lot of error messages, new DLL module names and many new malware emerging day by day.

From Internet Explorer 4.x onwards, the Browser Helper Objects feature was brought in, which facilitated programmers to extend the functionality of Internet Explorer for a good cause. At the same time, we see a lot of malware Browser Helper Objects affecting the functionality of Internet Explorer. From end-user point of view, the first and the only step they take is reinstalling Internet Explorer, which does not help in removing the add-ons. Another point is that the end-user had no clue of what add-ons are loaded into Internet Explorer, without using a third-party tool. As a result, add-on management task was difficult.  Some of the third-party utilities which display the browser add-ons are:

BHODemon -  Lists the BHOs installed and provides information about the control

HijackThis  -  Tracks each and every browser add-on, search settings etc

ToolbarCop -  The utility which I wrote, facilitates removal of toolbars, toolbar buttons, Browser Helper Objects (ability to disable them),  context-menu extensions.

Microsoft Knowledgebase articles regarding third-party add-ons

Error Message: Iexplore.exe Has Generated Errors and Will Be Closed By Windows
Versions of Comet Cursor That Are Earlier Than Version 4.0 Cause an Error Message
Invalid Page Fault Error Messages If You Run Internet Explorer 5.5 and Aureate Radiate
Bhodisp0.dll or Bhodisp.dll Cause an Error Message in Windows XP
"Iexplore.exe has encountered a problem and needs to close" error message when you try to start Internet Explorer
Unexplained computer behavior may be caused by third-party software
Error Message: Invalid Page Fault in Module Wtieclient.dll
Random General Protection Faults with Comet Cursor Version 1.5 Installed
Microsoft Online Crash Analysis - Error: Wurld Media Client

Internet Explorer 6.0 introduced a feature wherein the third-party browser extensions (Toolbars, BHOs) could be disabled entirely. The major disadvantage here is the user cannot selectively enable or disable a particular add-on. This is a good feature improvement over the earlier versions of Internet Explorer. Still, the user has no clue of what add-ons are loaded without his knowledge. The only clue is the error message and the module name (filename.DLL) seen on the Error-Report dialog.

Now comes the "Manage Add-ons" feature in Internet Explorer Windows XP SP2. The "Manage Add-ons" dialog lists all the third-party browser extensions installed in Internet Explorer and provides the ability to disable them selectively. The add-ons may be in the form of:

Browser Helper Objects
ActiveX controls
Toolbar extensions
Browser extensions

If an add-on is disabled, Internet Explorer adds the CLSID control to the don't load (a naming convention I use) list in the registry. Upon launching a new instance of Internet Explorer, the don't load list is checked by iexplore.exe (and explorer.exe) processes and it never loads that control.

Another interesting feature is that you can use Show to control the way in which the add-ons list is displayed. It has two options:

Add-ons currently loaded in Internet Explorer. This option lists the add-ons that have been instantiated (or loaded into memory) within the current Internet Explorer process and those which have been blocked from instantiating. This includes ActiveX controls that were used by Web pages that were previously viewed within the current process.

Add-ons that have been used by Internet Explorer. This option lists all add-ons that have been referenced by Internet Explorer and are still installed.

"Manage Add-ons" feature cannot be used to delete an add-on, you can only enable/disable the items.  The add-ons which you've disabled are added to the exclusion list here:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext\Settings

Example: A sample CLSID control (Adobe Acrobat's BHO) blocked:

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext\Settings\{06849E9F-C8D7-4D59-B87D-784B7D6BE0B3}] 
"Flags"=dword:00000001 
"Version"="*"

IEAdd.JPG (67566 bytes)

Overall, it's a good feature in XP SP2. There are much more enhancements apart from the Add-ons feature.

References

Changes to Functionality in Microsoft Windows XP Service Pack 2

Manage Internet Explorer Add-ons using Group Policy