Smart Contract Security: Understanding Security in Web3

5 min readMay 25


Smart contracts are automated programs that make agreements easier. They work on blockchain networks. Blockchains are ledgers that are open to all but can’t be retroactively changed.

Smart contracts can be used for trading, managing financial transactions, and enforcing legal agreements. Because they’re digital, smart contract security becomes crucial.

What is Smart Contract Security?

Smart contract security is about preventing unwanted access, change, or theft. These contracts automate the agreement terms, including digital asset transfers. They can’t be changed once they’re on the blockchain network.

Platforms like NFTs, DeFi, and all of Web3 use smart contracts. With billions of dollars involved, smart contract security is key. In 2022 alone, about $3.7 billion was stolen from Web3 protocols and users.

As blockchain is still evolving, challenges like scalability, interoperability, and privacy need to be tackled. Smart contract security is crucial to this, as it helps prevent attacks and ensures network integrity.

Risks to Smart Contract Security

Smart contract security risks can come from various factors like code bugs, blockchain vulnerabilities, and programming language flaws. Once a contract is deployed and becomes unchangeable, any security issues can be used by attackers to steal or disrupt the contract.

Coding errors are one significant risk to smart contract security. Smart contracts are created using languages like Solidity. It’s new, and developers may not fully understand it. This can lead to errors that attackers can exploit.

A 51% attack on the blockchain network is another risk. In this, an attacker controls over half of the network’s computing power. They can manipulate transactions and create false ones. This can harm smart contract security by leading to asset theft or contract changes.

Boosting Smart Contract Security

Several measures can improve smart contract security. These include:

  1. Code Auditing: Checking the smart contract’s code to find and fix errors or vulnerabilities.
  2. Penetration Testing: Trying to exploit the contract’s security vulnerabilities to find weak points in its design.
  3. Formal Verification: Using math to confirm that the smart contract works correctly in all possible situations.
  4. Multi-Signature Wallets: Needing more than one person to approve a transaction or contract change. This can help avoid unwanted access and add a security layer.

Smart Contract Security Best Practices

In addition to these measures, some best practices can enhance smart contract security:

  1. Following the Principle of Least Privilege: A contract should only have necessary permissions. Limiting access can minimize potential damage from a breach.
  2. Using Open-Source Libraries: These can reduce coding errors and security vulnerabilities. Developers should review the code to ensure it fits their project’s needs.
  3. Implementing a Timelock: A timelock delays a transaction until a specific time, adding an extra security layer.
  4. Testing on a Testnet: Developers should test the contract on a testnet before launching it on the mainnet. This can help spot potential issues.
  5. Using a Bug Bounty Program: This program encourages ethical hackers to find and report security issues, thus strengthening smart contract security.

As we delve deeper into the topic of smart contract security, we need to understand some common vulnerabilities. One such threat to smart contract security is a reentrancy attack. In a reentrancy attack, a malicious contract interrupts an external contract during execution. It does this by initiating an external call back to the original contract before it has finished executing.

This disrupts the Ethereum Virtual Machine’s process, resulting in the malicious contract executing commands out of order. This can potentially lead to the theft of funds or other malicious actions.

External contracts themselves can pose a risk. These contracts are called by a smart contract to execute certain functions. The danger lies in the fact that the smart contract has no control over what the external contract does.

It can create a vulnerability, particularly if the external contract has been compromised. This illustrates the importance of careful programming and meticulous smart contract security audits.

A common issue during the development phase is dealing with overflows and underflows. In computer programming, an overflow occurs when a value is too large to be stored in the allocated memory, and an underflow happens when a value is too small. Both can lead to unpredictable outcomes in the smart contract, which can be exploited by attackers. Smart contract security audits can identify these risks and propose solutions before deployment.

Addressing these smart contract vulnerabilities requires robust smart contract security best practices. One such practice is to perform comprehensive security audits. These audits assess the contract’s code for potential risks and identify areas for improvement. They also look for possible ways an attacker might exploit the contract, such as through a reentrancy attack, or by exploiting overflows and underflows.

Another smart contract security best practice is to reduce reliance on external contracts, or if they are necessary, to ensure they are also subjected to thorough security audits. It’s vital to confirm the security of all interacting components in the contract ecosystem.

A secure development lifecycle is also crucial. This approach ensures that smart contract security considerations are integrated into every stage of the contract’s development, from design to deployment. This makes the contract more robust and reduces the likelihood of a successful attack.

By implementing these best practices, developers can ensure they are addressing smart contract security at every level, making it much harder for malicious actors to exploit their contracts.

Why You Need a Smart Contract Security Expert

To secure your smart contracts, you need a Web3 security expert. Smart contract security is different from non-blockchain security:

  1. Immutable Nature: Once a smart contract is on the blockchain, it can’t be changed. This means any issues can’t be fixed, and any locked funds may be lost forever.
  2. Limited Programming Languages: Smart contracts are typically written using specific languages. These languages have unique features that developers need to be cautious with.
  3. Decentralization: Smart contracts work on a decentralized network, which means there’s no overseeing authority. This can make it hard to detect and stop security breaches.
  4. Economic Incentives: Smart contracts usually involve money, which can attract people looking to exploit vulnerabilities.
  5. Smart Contract Auditing: This is a complex process that requires deep knowledge of blockchain technology and software security best practices.

In summary, smart contracts have great potential. But with that comes unique security vulnerabilities. Measures such as security auditing, penetration testing, formal verification, multi-signature wallets, and more, can mitigate these risks.

By focusing on these aspects, we can protect digital assets and ensure the safe use of smart contracts. At CertiK, our mission is to secure the Web3 world, with smart contract security at its core.