Immutability refers to the property of data being irrevocably codified in the shared data ledger of a blockchain network once a transaction has been successfully completed. The vast majority of non-blockchain computer networks are changeable, which means that the information contained inside them may be changed, censored, or controlled by a central authority or organization. Immutability enables a blockchain network to guarantee the overall trust and integrity of data for a decentralized application (dApp), platform, or coin by preventing data from being changed.
Immutability is a key property of a blockchain—and is one of the reasons the technology is so often associated with finance. If transactions are immutable, they cannot be altered or repudiated by the parties involved. This provides the trust and security needed for complex transactions.
Thanks to blockchain’s decentralized public ledger, a data breach is impossible to pull off. Data stored on an immutable blockchain platform can never be erased or overwritten. An attacker would need to control more than 50% of the network power in order for their forgery to outpace the legitimate copy and for the fake transaction histories to be considered the correct ones.