Hello @KevinS6913 ,
The list is yours to import/export and manage as you see fit. We wouldn't have a way to copyright-claim a contact list, as you are the sole owners of your lists - we merely host them in our server for ease of sending and management. The only thing we'd do with your list is automatically remove contacts that unsubscribe from the lists they were on, and set them aside within your account.
If you're curious about what account security we provide, I'd recommend checking out this article. Your users, especially your account owner, should also be performing basic account security practices regarding their login info. Some other helpful articles, if you'd like to know what some of those basic account security practices are: