A Quick Guide to Smart Contract Security

A Quick Guide to Smart Contract Security

In the realm of Web3, smart contract security plays a vital role, yet it is often given less attention compared to smart contract development skills. This has resulted in significant financial losses due to minor errors, oversights, and even mistakes borne out of ignorance.

The CyberNews.com investigation team’s analysis of Ethereum smart contracts shows that nearly 3,800 smart contracts have severe weaknesses that can allow cybercriminals to quickly steal 1 million dollars. One of the most famous Ethereum smart contract vulnerabilities is what’s known as a reentrancy attack, which in 2016 allowed a cybercriminal to steal $50 million.

Recent instances of smart contract vulnerabilities and hacking incidents have shed light on the urgent need for improved security practices within the industry.

Understanding Smart Contracts

At its core, a smart contract is a self-executing agreement built on a blockchain network. It is made up of a piece of code that establishes and enforces the terms and conditions of an agreement without requiring intermediaries. Smart contracts offer transparency, immutability, and efficiency, making them highly sought-after for various applications such as decentralized finance (DeFi), non-fungible tokens (NFTs), and supply chain management, etc.

What is the Essence of Smart Contract Security

Smart contract security revolves around safeguarding smart contracts from vulnerabilities and exploits that could lead to unauthorized access, manipulation, or fund theft. Ensuring the security of smart contracts is vital for maintaining trust in decentralized applications (dApps) and the overall blockchain ecosystem. By implementing robust security measures, developers can mitigate the risks associated with potential vulnerabilities.

Examples of Losses Due to Smart Contract Breaches

There have been several notable incidents that vividly demonstrate the potential consequences of neglecting smart contract security. These stories serve as reminders to both developers and users to prioritize strict security measures. Here are three of such examples:

  • AkuDreams Bug and Exploit:

In 2022, the AkuDreams development team encountered a significant setback due to a smart contract bug, resulting in a loss of $33 million. The incident occurred over a weekend, casting a shadow over the highly anticipated nonfungible token (NFT) project known as Akutars. Surprisingly, the loss was not caused by a malicious hack but rather by a combination of an exploit and a bug within the smart contract.

The exploit that unfolded during this unfortunate event was not driven by an intention to pilfer funds. Instead, it was carried out by an individual aiming to highlight a vulnerability present within the project. Nonetheless, the consequence was severe, with approximately 11,500 Ether, equivalent to nearly $33 million, becoming permanently locked within the smart contract. Regrettably, this rendered the funds inaccessible even to the development team, leaving them in a precarious situation.

Instances like this serve as reminders of the critical importance of rigorous smart contract security measures. The incident underlines the need for thorough testing, audits, and comprehensive bug-fixing processes to identify and rectify potential vulnerabilities before deploying a smart contract.

  • Zeed Protocol Exploit:

Still in 2022, an individual with malicious intent seized an opportunity to exploit a vulnerability within this protocol's reward distribution mechanism. By exploiting this weakness, the attacker was able to generate additional tokens, which were subsequently sold, resulting in a drastic crash in the token price, effectively reducing it to zero. However, the attacker's gain amounted to just over $1 million.

To carry out the exploit, the stolen cryptocurrency was transferred to an "attack contract". An attack contract is a smart contract that automatically and quickly executes a found exploit. Interestingly, in a twist of events, it appears that the attacker's excitement over the successful heist led to an oversight. They neglected to transfer the stolen crypto, valued at over $1 million, out of their attack contract before initiating its self-destruction. As a result, the funds became irretrievable and permanently locked within the contract, rendering any movement or recovery impossible.

  • Deus Finance exploit:

Deus Finance was also exploited in 2022, resulting in over $3 million in losses in Dai (DAI) and Ether. The attackers skillfully exploited and manipulated the lending contract of the protocol, which was used to establish a price oracle for its flash loans. This malicious action had severe repercussions, ultimately resulting in the insolvency of users' funds.

The attack on Deus Finance serves as a stark reminder of the importance of robust security measures within decentralized finance (DeFi) protocols. Such incidents highlight the vulnerability of complex financial systems and the critical need for constant vigilance and auditing to identify and mitigate potential exploits.

Essential Measures to Enhance Smart Contract Security

To enhance the security of your smart contracts, it is crucial to consider the following aspects:

  1. Knowing Possible Smart Contract Vulnerabilities: To enhance the security of your smart contracts, it is crucial to have a deep understanding of potential vulnerabilities that can be exploited. Common vulnerabilities include reentrancy attacks, integer overflow and underflow, unchecked external calls, and insecure randomness generation, etc. By familiarizing yourself with these vulnerabilities, you can take proactive measures to address them during the development and auditing stages. I have an entire series on smart contract vulnerabilities; the goal is to publish at least 30 of them. Click here to read them.

  2. Code Audits: Before deploying your smart contracts, conduct comprehensive audits to identify any vulnerabilities or weaknesses in your smart contract code, whether through experienced auditors or security or auditing firms that specialize in smart contract audits. This can help uncover potential security flaws and provide recommendations for improvement, ensuring that your smart contracts are robust and resistant to attacks.

  3. Secure Coding Practices: Follow secure coding practices throughout the entire development process. Implement best practices such as checking against re-enterancy, proper error handling, checking ownership before transferring funds, secure contract design patterns, etc. Adhering to established coding standards and frameworks significantly reduces the likelihood of introducing security flaws.

  4. Rigorous Testing and Testnet Deployments: Before deploying smart contracts on the mainnet, ensure thorough testing on blockchain test networks such as Ethereum's Sepolia or Goerli. Thoroughly test your smart contracts using various scenarios and edge cases. Test both the expected behavior and potential vulnerabilities. This practice enables the identification and resolution of potential issues before real funds are at stake.

Other Tips and Techniques for Smart Contract Security

Here are some additional tips and techniques to bolster the security of your smart contracts:

  • Regularly update your contract's dependencies to leverage the latest security patches.

  • Implement access control mechanisms to restrict unauthorized interactions.

  • Utilize multi-signature wallets or employ timelock mechanisms to prevent single points of failure.

  • Stay updated with the latest security practices and informed about developments in the smart contract space.

  • Actively engage with the broader smart contract community through forums, developer communities, and security-focused channels. Sharing knowledge and learning from others' experiences is invaluable in improving security practices.


Recent incidents of smart contract vulnerabilities and breaches have underscored the significance of prioritizing robust security measures. By comprehending the potential vulnerabilities, adhering to best practices, conducting thorough audits, and remaining informed about the latest security advancements, developers can significantly enhance the security of their smart contracts.

It is essential to recognize that the responsibility for smart contract security extends to developers, auditors, and users alike. By fostering collaboration, sharing knowledge, and continuously improving security practices, we can create a more secure and resilient Web3 environment.

Thanks for reading.

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