All depends if you mean data security or "user" security
The guide specified by Nicolai covers it all, everything from end to end encryption to firmware tape encryption (best option!) but if you need to lock down users you reall need to use NBAC (NetBackup Access Control) - you really do need to carefully go through the guide if that is what you need though as there is quite a lot to it
On the other hand you could just keep people out of your NetBackup server all together (apart from dedicated admins) and let others use OpsCenter which it is much easier to setup users and their rights and a lot of management, reporting and even restores can now all dbe done from OpsCenter:
http://www.symantec.com/docs/DOC5042
Hope this helps
