15 Security Best Practices Every Blockchain Developer Should Know

Building a smart contract is only half the battle. The real challenge is making sure your contract stays safe every single moment it’s live on the blockchain. A single exploit can cost you and your users enormous losses—financial, reputational, and more.

In this guide, we explore how to protect your decentralized applications (dApps) with easy-to-understand, proven security practices.

1. Stick to Well-Known Libraries

• Why It Matters: Established libraries (like OpenZeppelin) undergo heavy testing and audits, reducing your chances of introducing vulnerabilities.
• What To Do: Whenever possible, reuse battle-tested code (e.g., ERC20, ERC721, Ownable). These libraries have been scrutinized by many developers, so they’re safer out of the box.

2. Keep It Simple

• Why It Matters: Complex code is hard to audit, test, and maintain.
• What To Do: Split big contracts into smaller, focused ones. Each contract should do one thing well. Fewer lines of code mean fewer places for bugs to hide.

3. Use Proper Access Control

• Why It Matters: A malicious user with admin powers can ruin everything.
• What To Do: Rely on Ownable or AccessControl from OpenZeppelin. Make sure only trusted roles can call sensitive functions. Never use tx.origin to check for the sender—stick with msg.sender.

4. Stop Reentrancy Attacks

• Why It Matters: Reentrancy lets attackers call your contract’s function again (and again) before the first call finishes, causing serious damage.
• What To Do:
  1. Use the checks-effects-interactions pattern.
  2. Update state first, then interact with external contracts or transfer tokens.
  3. Include nonReentrant modifiers (e.g., ReentrancyGuard).

5. Watch Out for Arithmetic Overflows

• Why It Matters: Adding or subtracting past the maximum integer value can wrap numbers around, creating big problems.
• What To Do:
  • Use SafeMath (built into Solidity 0.8.x).
  • Carefully handle edge cases in your arithmetic.

6. Validate All Inputs

• Why It Matters: Attackers can pass invalid data—like zero addresses or manipulated parameters—to mess with your contract.
• What To Do:
  • Use require to check that inputs are valid.
  • Double-check return values from low-level calls (like .call()).

7. Don’t Rely on Block Variables for Randomness

• Why It Matters: Blockchain data (like block.timestamp, block.number, blockhash) is public, making it easy to predict or influence “random” outcomes.
• What To Do:
  • Use trusted solutions like Chainlink VRF for secure randomness.

8. Never Store Private Data On-Chain

• Why It Matters: Everything on a public blockchain is visible—if you store secrets in your contract, they’re no longer secrets.
• What To Do:
  • Handle private keys or sensitive info off-chain.
  • Consider privacy solutions like zk-SNARKs if you really need on-chain privacy.

9. Test Thoroughly

• Why It Matters: Testing is often the difference between a bulletproof contract and one waiting to be exploited.
• What To Do:
  • Use frameworks like Hardhat, Truffle, or Foundry.
  • Write tests for both normal conditions and weird edge cases.
  • Try fuzzing and property-based testing with tools like Echidna to push your contract to its limits.

10. Audit and Review Regularly

• Why It Matters: A second set of eyes (or a third, or a fourth) can catch potential exploits you missed.
• What To Do:
  • Run static analysis tools (e.g., FailSafe Auditor AI, Mythril).
  • Get professional audits for high-value projects.
  • Launch bug bounties to encourage ethical hackers to report issues.

11. Handle Upgrades with Care

• Why It Matters: Upgradeability can fix bugs and add features, but it brings risks like storage collisions and new vulnerabilities.
• What To Do:
  • Use trusted proxy patterns from OpenZeppelin’s Upgradeable Contracts.
  • Keep storage layout consistent to avoid overwriting critical variables.
  • Limit who can perform upgrades (e.g., only a multisig admin with FailSafe Guard).

12. Implement Timelocks and Pausable Functions

• Why It Matters: Timelocks warn your users before big changes happen, and pausing lets you freeze actions in emergencies.
• What To Do:
  • Use a TimelockController for governance.
  • Add a Pausable modifier to critical functions so you can quickly suspend them if you spot trouble.

13. Be Careful with Fallback and Receive

• Why It Matters: If someone accidentally sends Ether or triggers fallback logic, your contract could break if you’re not prepared.
• What To Do:
  • If your contract shouldn’t hold Ether, revert any Ether in fallback() or receive().
  • If it does hold Ether, make sure to handle and log it properly.

14. Don’t Hardcode Addresses

• Why It Matters: Contracts and APIs can change, and addresses on different networks might not match.
• What To Do:
  • Use constructor parameters or immutable variables to store addresses.
  • If possible, have an admin function (with tight access control) to update addresses.

15. Layer Your Security

• Why It Matters: No single feature can prevent all attacks. Multiple layers (multisigs, audits, circuit breakers, etc.) reduce the chance of a catastrophic failure.
• What To Do:
  • Use multisig wallets like FailSafe’s Access Control Guard for admin privileges.
  • Monitor your contract’s activity with FailSafe Monitor AI.

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Don’t Just Build Secure Contracts—Stop Attacks in Real Time with FailSafe

Even the tightest security measures can’t stop every threat—especially when malicious actors learn new tricks every day. That’s where FailSafe steps in to protect your blockchain project around the clock.

FailSafe lets you:

• Respond to Attacks and Prevent Fraud in Real-Time: Instantly detect suspicious activities and take action before damage is done.
• Monitor, Detect, and Eliminate Risks: It’s like having a 24/7 security team for your smart contracts, wallets, and entire blockchain.
• Enhance Trust, Compliance, and Peace of Mind: Prove to users and regulators that you’re serious about keeping their assets safe.

Ready to take the next step? Build secure smart contracts using these best practices, then empower them with FailSafe. When the bad guys strike—and they will—make sure you’re prepared to shut them down, fast. Keep your funds, reputation, and community safe by combining strong code with real-time protection.