Web3 promises decentralized, transparent systems. But with that power comes a new breed of vulnerabilities — from re-entrancy attacks in smart contracts to logic flaws in dApps. Traditional pen-testing techniques only go so far in blockchain ecosystems.
In this post, we’ll walk through a structured approach to penetration testing for Web3 applications, with a focus on smart contract security, decentralized applications (dApps), and Layer 1/2 networks.
🧠 Why Penetration Testing in Web3 is Different
Web3 applications introduce unique risks:
- Smart contracts are immutable — vulnerabilities, once deployed, cannot be patched like traditional code.
- Money is directly at stake — one bug could drain millions.
- Security is public — exploits and hacks are permanent and visible on-chain.
That’s why a specialized pentest is essential before deployment.
🧪 Step-by-Step Pentest Process for Web3 & Smart Contracts
🔍 Step 1: Scoping the Assessment
Start by understanding the architecture:
- What chain are you deploying on? (Ethereum, BNB, Polygon, etc.)
- What smart contracts are in scope?
- Are there any external contract interactions or oracle dependencies?
- Is the frontend centralized or IPFS-based?
Deliverable: Threat model + test scope document
🧰 Step 2: Set Up Your Tooling Stack
Here’s the essential toolset for a Web3 pentest:
🛠 Smart Contract Analysis
ToolPurpose
Slither Static analysis for Solidity
Mythril Symbolic execution + detection of reentrancy, overflows
Echidna Property-based fuzzing for smart contracts
Manticore Concolic analysis for EVM bytecode
Oyente Early open-source analyzer
🔧 Manual Code Review Tools
- VSCode + Solidity extension
- Surya (visualize contract call graphs)
- Solhint (lint Solidity code for best practices)
🧪 Web3-Focused Testing Platforms
- Foundry (fast unit testing framework in Solidity)
- Hardhat (test scripts + local blockchain + debugger)
- Ganache (local test blockchain)
🧱 Network Interaction Tools
- Tenderly (simulate transactions and track reverts)
- Etherscan + BlockScout (contract verification and tx trace)
- Remix IDE (great for manual interaction and simulation)
🔐 Frontend & dApp Testing
- Burp Suite / OWASP ZAP (if dApp calls centralized services)
- WalletConnect/Fake Signers (for simulating user interaction)
- Metamask + Hardhat Fork Mode (to test against live chain data)
🔓 Step 3: Attack Surface Mapping
- Identify public/external contract functions.
- Map dependencies: other contracts, tokens, LPs, or oracles.
- Look for upgradeability patterns: proxies, delegatecall, storage collisions.
- Analyze access control: onlyOwner, msg.sender, multisig management.
Deliverable: Call graph + entry point analysis
🔥 Step 4: Exploit Simulation and Testing
Perform tests against:
- Reentrancy
- Integer overflows/underflows (even with SafeMath)
- Unprotected delegatecall / selfdestruct
- Gas griefing / denial-of-service
- Flash loan exploit simulation
- Time manipulation (block.timestamp)
Tools like Foundry’s forge test, Echidna, and Slither’s detectors help automate this.
🧾 Step 5: Reporting and Remediation
Your report should include:
- Executive Summary
- Vulnerability list: severity, impact, proof of concept
- Recommendations: mitigation strategies, updated code samples
- Verification step: post-fix retest
Use CVSSv3 or a custom scoring matrix. Offer a retest phase to validate fixes.
🛡️ Advanced Techniques (Optional)
- Formal Verification: Use Certora or Securify for mathematical proofs of safety
- zkAudit Trail: If ZKPs are involved, validate proof circuits
- On-chain Simulation: Use hardhat-fork to simulate mainnet-based attacks
🧠 Best Practices for Web3 Security
- Use audited libraries only (e.g., OpenZeppelin)
- Avoid upgradability unless necessary
- Implement pause/kill switches for emergency response
- Automate tests in CI (e.g., slither + forge test on every push)
- Never assume msg.sender is a user — attackers can simulate anything
💼 Real-World Use Cases
- Auditing DeFi yield farms for reentrancy and under-collateralization
- Simulating oracle price manipulation in lending platforms
- Testing NFT contracts for overmint or underpriced auction edge cases
- Reviewing multisig wallet controls for governance contracts
🚀 Final Thoughts
Smart contract pentesting isn’t just security — it’s protecting assets, reputations, and the future of decentralized tech. With billions locked in DeFi and NFTs, the margin for error is zero.
