There is a way to turn off HTTP codebases on the Notification Server and Package servers.
In the coresettings.config files, an entry can be changed that will stop any Agents or Package Servers from downloading from the Notification Server using HTTP.
In order to avoid corruption on the actual coresettings.config file, try to use NSConfigurator. Open it by going to Start > All Programs > Altiris > Tools > NS Configurator. If you don't have it installed, search for NSConfigurator.msi. Usually it is located at C:\Program Files\Altiris\Diagnostics. When you have opened NSConfigurator, look for Get Package Info Settings, and the key is called GenerateNSHTTPPackageCodebases. Change it from 1 to 0. Apply changes.
To prevent Package Servers from publishing HTTP codebases for downloaded packages, go to Configuration tab > Package Server > Settings tab. Under Published Codebase Types, Disable Publish HTTP codebases.
This will cause only UNC codebase to be generated for downloaded packages, stopping the Package Server from including HTTP codebase in its reported Package summary event. Consequently, the NS will not receive and store the HTTP codebase and will not hand out the codebase to agents when they request package sources.