Node Access Question

First let me say that I've read the module developers handbook, but overall, I'm new to Drupal development. This is my first module. I want to know if there is a hook in the module that cann be used to grant to deny access to every type of node. I know by default, the modules node_access() hook can be used for the type of content they provide, but can that be changed to grant access to all types of nodes (of course, with the node type passed in). If this is possible, any pointers to existing code would be greatly appreciated.

If what I want is not possible, would I then have to modify the drupal node module? I would like to avoid that.

Regards,
Kory