Access to your attic should be inside your security perimeter; in the garage or an interior space. If you have an external access door, consider having it professionally removed and the opening permanently sealed; there is no effective way to adequately secure such an opening.

     The same applies to hatches to crawl spaces (externally-applied padlocks are much too easy to defeat to provide any but the most temporary security), and outside hatchways to basements (although modern all-steel hatchways usually are capable of being adequately secured from inside, and not very vulnerable to manipulation or defeat from outside).