Blockchain technology's immutable and transparent nature makes it incredibly difficult for attackers to manipulate transactions without being detected, thereby preventing fraud. Here are some ways blockchain prevents fraud:

1. *Immutable ledger*: Transactions are permanently recorded and cannot be altered or deleted.

2. *Transparent transactions*: All transactions are publicly visible, making it difficult to conceal fraudulent activity.

3. *Consensus mechanism*: Network consensus ensures that all nodes agree on the state of the ledger, preventing a single entity from manipulating transactions.

4. *Cryptographic hashes*: Transactions are linked together using hashes, making it impossible to alter a transaction without being detected.

5. *Smart contract automation*: Automated contracts execute transactions without intermediaries, reducing the risk of fraudulent activity.

By preventing fraud, blockchain technology builds trust and confidence in the transaction process, protecting users and organizations from financial losses and reputational damage.