# Prominent Contract Hacks

Smart contracts have become increasingly popular in the world of blockchain and cryptocurrencies. These self-executing computer programs are designed to enforce the terms of an agreement between parties. However, smart contracts are not immune to hacking and security breaches. In this article, we will discuss some of the most prominent smart contract hacks and how they could have been avoided.

1. The DAO Hack: The DAO was a decentralized autonomous organization built on the Ethereum blockchain. In 2016, an attacker discovered a vulnerability in the smart contract code and stole approximately $50 million worth of Ether. The hack occurred because the smart contract lacked a simple security check known as a "recursive call" protection. This protection would have prevented the attacker from draining the funds repeatedly.
2. Parity Wallet Hack: In 2017, a hacker exploited a vulnerability in the Parity wallet's smart contract code and stole over $30 million worth of Ether. The vulnerability allowed the attacker to take control of the wallet's contract and transfer the funds to their own address. The vulnerability was a result of a coding error and could have been avoided with proper security testing and code review.
3. Bancor Hack: In 2018, the Bancor exchange suffered a hack that resulted in the loss of $13.5 million worth of cryptocurrencies. The hack was able to occur because the smart contract lacked proper access controls, allowing the attacker to transfer the funds from the exchange's wallet. Proper access controls and security measures could have prevented this attack.
4. ZeppelinOS Hack: In 2018, the ZeppelinOS platform was hacked, resulting in the loss of over $1 million worth of Ethereum. The vulnerability was a result of a coding error in the platform's smart contract code, allowing the attacker to execute malicious code. The vulnerability could have been avoided with proper security testing and code review.
5. Ponzi Schemes: Ponzi schemes are fraudulent investment schemes that are often facilitated by smart contracts. These schemes rely on new investors to pay off older investors, leading to eventual collapse. Ponzi schemes can be prevented by conducting due diligence on the smart contract code and the team behind it, as well as thoroughly researching the investment opportunity.
