Bitcoin is still new to most of us, just like internet was back in the 1990's. Back then, people were giving away their credit cards in fake websites. So you still need to be very careful how you use your bitcoins and how you use your private keys. Rule number ONE: Keep you private keys PRIVATE. You don't go around showing your passwords.
The rules of how Bitcoin works is different from traditional financial system. In traditional financial system, we have a part of gold sitting in a bank, and the bank provides us with credit and debit cards so that we can easily take out money whenever we need it. The big difference, we have recourse with your credit or debit cards if someone steals my credit card, and makes a transaction, I can always call the bank and report the theft. And they can give you your money back, of course after investigation. But with Bitcoin, if someone steals your bitcoins, there is NO RECOURSE. That money is gone. There is no way of getting that money back.
People in the Bitcoin community are creating ways to prevent your money sitting in a vault from being taken out. But you still have some money set aside for your day to day spending. That where a lot of innovations in the Bitcoin community security is coming. They separated this concept of Hot wallet for day to day spending and Secured wallet for yor savings. By using tools like Two factor authentication, 2 day delay, Multi-signatures aka multisig wallets, it is very hard to take the money out from the Secured wallet. Multi-signatures wallets require two or three signatures (multiple parties) to authorize a Bitcoin transaction. These parties can be people, institutions or programmed scripts.
Corporations like CoinBase which hold your private keys and hundred of millions of dollars use a technology called Hot and Cold storage.
- Cold storage refers to bitcoins kept offline (eg. bitcoins kept on a USB drive or a dedicated hardware wallet). Its account for about 97% of all Bitcoins
- Hot wallet or storage (internet connected) refers to the method by which every bitcoin exchange keeps a certain liquidity just in case there is a massive influx of withdrawal requests. Account for about 3% of Bicoins.
Is Bitcoin really Secure? Up to everyone to decide