For reliable protection of your main assets, we use the technology of cold and hot wallets. Hot wallet is used during transactions, and there is always a small amount of assets on it. As opposed to hot wallet, cold wallet is used for storing the main bulk of your funds, and, since it is not connected to the Internet, there is absolutely no access to it from the outside. This method of storage is probably the safest.
An additional layer of security is the MultiSig technology. This is a configuration that applies certain protection on the wallet, where several electronic keys are required to confirm the transaction. These keys, or signatures, are not stored on the server. Requiring more than one cryptographic signature to transfer funds, MultiSig wallets provide enhanced security.
However, no matter how well protected your funds are, the responsibility for their storage lies entirely with you. No protection is safe enough if the user is careless about security issues.
You can learn about how to increase the security of your account here.