There's no software hack floating around in cyberspace that will allow you to view private Facebook profiles... If you want to gain view permission to a private Facebook profile in 2015 you are going to have to request it.
However, you could always send a friend request using a fake profile if you just wanted to hide your identity.
Alternatively, you can see private Facebook profiles by asking to login as a friend of the user, who has private access.
These are the two least complicated and most effective ways to view a private Facebook profile without explicit permission.
Anythign else is likely to fail, and may end in a malware virus being installed on your device instead.
Think about it... If someone is willing to create software to hack people's Facebook account, who says they wouldn't hack your account when you download it too? Or worse... Your personal files and bank details? Browsing history...