Smart Contract Security: A Taxonomy of Vulnerabilities, Attacks, and Defenses
Smart contracts are self-executing programs deployed on a blockchain that automatically enforce the terms of an agreement without an intermediary. Since their introduction on Ethereum in 2015, they have enabled decentralized exchanges, lending protocols, NFT marketplaces, on-chain governance systems, and many other decentralized applications.
But the same properties that make smart contracts powerful also make their bugs dangerous. They are immutable, transparent, and autonomous. Once a vulnerable contract is deployed, it cannot always be patched easily. Anyone can inspect its bytecode and search for weaknesses. And because contracts often custody user funds directly, one flaw can drain millions of dollars in minutes.
History has shown this repeatedly. The 2016 DAO hack exploited a reentrancy vulnerability to siphon millions of ETH and triggered the Ethereum hard fork. The 2021 Poly Network attack abused broken access control and resulted in one of the largest DeFi exploits in history. Many flash loan attacks...
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