Each node in the system is in charge of storing, communicating, and preserving blockchain data.
Unlike traditional record-keeping systems where a central database or server manages all transactional activities, blockchain doesn’t rely on a centralized database. Instead, data is stored in blocks that make up a blockchain across a decentralized network of computers or servers, also called nodes. All nodes are interconnected and constantly exchange the latest blockchain data to keep them up to date. Each node in the system is in charge of storing, communicating, and preserving blockchain data.
In other words, blockchains are distributed across different secure digital spaces, and thanks to this distributed nature across a peer-to-peer network, there is no central point for hacking or attacking. If any node’s data is attacked and altered undesirably, or suddenly becomes inactive, other nodes will preserve the integrity. Operations on nodes employ the consensus mechanism in which a block(storing transactional data) is validated by its hash before being added to a blockchain. If data is altered, the system will detect it and the validation fails. As a result, the affected block won’t be added to the blockchain (or written into the database).
If a hacker attacks a blockchain, the computing power and resources required to access every node and alter every block in the blockchain are enormous. From the genesis block (the very first block) to the most current block, for a hacker to touch all blocks simultaneously, they would need to sneak through the security or firewall system of the servers. Commercial firewalls are multi-layered security systems that are not easy to penetrate. The larger the blockchain (more blocks) or the more nodes (more distributed copies) the blockchain has, the much harder it is to launch a successful attack.