SharePoint - Removing User Alerts

Here are the paths to removing and changing "alerts" permission levels within the site collection.

Site Settings > Modify All Site Settings > Advanced Permissions > Settings > Permissions Levels >

Select the 'Read' permission level then unselect the 'Create Alerts' option.

This will stop all users with the 'Read' permission (usually all authenticated in a typical intranet deployment) from being able to create alerts, although users with the contribute, full control etc permissions will still be able.

You can disable the create alerts feature altogether from central admin by following these steps…

Central Admin > Application Management > User Permissions for Web Application

Unselect the 'Create Alerts' option.