Page injection

Hi folks,

In my final sem project, I have been asked to configure a firewall which inject a custom page overplayed over the intended page. For example, if user access site google.com, so now over the page google.com the firewall should be able to load a transparent consent page which user has to accept and then pass thru. also, this should repeat after every 30 mins.

Ian not sure how to do this, any help would be appreciated.

Thanks guys
Nandi.