Yes, blockchain networks can be hacked, though they are generally secure by design. The most common attack methods include:

1. 51% Attacks: When a single entity controls over half the network’s computing power, allowing them to reverse or block transactions (common in smaller blockchains).
2. Smart Contract Exploits: Bugs in smart contract code let hackers steal funds (e.g., the DAO hack).
3. Phishing/Scams: Tricking users into sharing private keys or passwords.
4. Sybil Attacks: Creating fake nodes to overwhelm or disrupt the network.
5. Code Vulnerabilities: Exploits in the blockchain’s core software (e.g., bugs in consensus mechanisms).

Human errors (like poor key management) and insecure third-party services (e.g., exchanges) are also weak points. While blockchains are resilient, no system is entirely unhackable—proper security practices are crucial.