There more chances of hacking if you are storing your bitcoins in online wallets and exchanges always keep in mind not to store your bitcoins on exchanges as there are more chances for you to loose bitcoins, not all wallets can be hacked, paper wallets, hardware wallets,USB wallets and Trezor are the safest wallets available in the crypto market. For buying and selling of bitcoins you need to use good reputed exchanges or else you might loose your bitcoins. Hackers can hack anything be it bitcoin wallets or the normal banking system when hackers attack banks the bankers will not be able to do anything, they might loose their customers trust and databases. To keep your bitcoins safe you need to store your bitcoins in cold storage's like USB devices, paper wallets and hardware wallets.