If I have a list of IPs in a MySQL that I want to not display certain content (AdSense ads), what would be the fastest way to do that? Put them in a text file via a cron job and check if it contains the IP, do a MySQL look up every time a page is loaded and index the IP column or what?

I'm going to need whatever I do to display on every page, or possible just store a session or something, but there will need to be some type of lookup.

Thanks for any advice.