Once a new block is added to the blockchain, it becomes publicly available for anyone to view. Its contents become very difficult to alter because of these hash codes. If a hacker attempts to edit your transaction’s information in any way, the hash code would change as well.
The next block in the chain will still contain the original hash, so the hacker would also have to update the next block too. In order to change a single block, a hacker would need to change every single block after it on the blockchain.
In other words, the chain’s information duplication function means that when a block is added to the blockchain it becomes very difficult to edit, relying on huge amounts of computing power to complete the multiplying complex problems.
Many believe cryptocurrency is the way of the future regarding secure and safe financial transactions. Its water-tight hash system, combined with other elements of blockchain technology, including a publicly-viewable ledger and system of verification functioning without the reliance of trust, means the system is almost impossible to manipulate.
Any hacks or breaches are almost always as a fault of the user's callousness, laziness or plain negligence, not the system itself.