Disable direct access to posts?

Im creating a site where in one part I have a custom post type, offers, which I want to create lists of offers with information from individual offer post displayed. Sort of like how most voucher sites work, where they display voucher details, but you cant acutually visit the ‘offer’ post directly..

How would I disable access to the post directly? Both for users and indexing/search engines?

Also, is this a bad way of achieiving this?