In order to prevent hackers from stealing your bitcoin, you have to choose a secure wallet. The security of choosing a majority of online Bitcoin wallets is questionable. Massive online wallet providers and bitcoin exchanges have suffered losses due to a variety of security breaches. If you must use an online bitcoin wallet service, use a dual authentication service to increase the security of your account.
You are right. We prevent hackers from stealing our coins. We need a lot of protection methods. The most up-to-date files are placed on a hard drive that is not connected to the network. Hackers can not take your coins away.