Private keys is very important  when it comes to keeping alt coins. You have to make sure that its stored at safest place . Don't give your laptop to people you don't trust. Stop installing softwares you dont trust and responding to spam mails. i won't stress much on that however i think its the private key hackers use to get into it. So they will do every thing to get it. Just make sure you are very strict when it comes to security and you will be fine trust me