At the high end of NFC communication you have the basically the same chips used in smartcards (like payment cards/sim cards/etc) running with limited power, but theoretically able to run all the same apps. These can be cryptographically secure.

At the other end, a lot of rfid tags are very easy to just read and clone, including many involved in access control systems. These often just work based on the uid number that is freely readable, and most of the protocols have chips available where the user can write this "globally unique" id that would normally be written by the factory.