Secure the Proxy Settings
After you enable the proxy settings, you should disable users’ ability to change them.
In the Group Policy window, in the left pane:
Select User Configuration.
Select Administrative Templates.
Select Windows Components.
Select Internet Explorer.
Select Internet Control Panel
Set Disable the Connections Page to Enabled.
Click Apply, and then click OK twice. Users now cannot change their proxy settings.
Group Policy for chrome and Firefox
Download the ADM files: You can download the latest files, including detailed documentation, at the following URL’s:
Download the zip file and then extract them to get the admx file, remember the path.
Open Group policy editor, edit the existing GPO or create a new one, then go to : User Configuration>Policies and right click on Administrative Templates. Select Add/Remove Templates… Click the Add… button and browse to where you extracted the chrome.adm file, select it, and click Open.
In the left panel tree view, navigate to User Configuration>Policies>Administrative Templates->Classic Administrative Templates. You will now see the new configuration settings for Google.
When you extracted the zip you should have noticed some extra VBS files; specifically firefox_login.vbs, firefox_logout.vbs, firefox_shutdown.vbs, and firefox_startup.vbs.
To make these configuration changes VB scripts are used to configure Firefox during login/logout/startup/shutdown. These scripts should be imported to their correct locations inside the Policy.
In Group Policy Management Editor, navigate to Computer Configuration>Policies>Windows Settings and select Scripts (Startup/Shutdown).