Ethical Hacking: Blockchain & Smart Contract Security 2025

Discover how Bitcoin's proof-of-work consensus validates transactions, the mining process, and rewards, and how consensus vulnerabilities can arise in blockchain networks.

Understand how miners use proof of work and hash rate to validate Bitcoin transactions, and how a 51% attack can manipulate the blockchain by controlling over half the network's power.

explore how a 51% attack arises when miners exceed 50% of the network hash rate, enabling blockchain manipulation and potential double spending on bitcoin through mining pools.

Explore how mining pools exceed 50% of hash rate to trigger a 51% attack, introducing the Nakamoto coefficient and implications for Bitcoin and Ethereum.

This lecture explains how 51% attacks can be mitigated by ensuring miners run updated Bitcoin Core software, preserving consensus, reducing vulnerable hash rate from outdated nodes.

Learn how Bitcoin's hashrate distribution affects the feasibility of a 51% attack, including half-threshold calculations and how small percentage increases can enable powerful blockchain and smart contract attacks.

Examine traditional denial of service attacks and distributed denial of service, analyzing how request floods disrupt web servers from a network perspective, and explore implications for blockchain and smart contracts.

Explore how a transaction flooding attack causes denial of service on blockchain networks by saturating the main pool, triggering network latency, congestion, and potential node or software crashes.

Analyze denial of service attacks at the smart contract level, including transaction flooding and distributed DoS via botnets, and learn prevention strategies.

Explore denial of service in smart contracts, including unexpected revert attacks and block gas limit DDoS, illustrated by a bank contract and a malicious inter-contract setup.

Demonstrate a denial of service attack on a bank smart contract through an attacker contract that disrupts the current biggest investor logic, exposing smart contract vulnerabilities.

Demonstrate a practical denial of service attack on a bank contract using an attacker contract to exploit the current biggest investor logic.

Explore the reentrancy attack theory and its practical demonstration on smart contracts, including the 2016 DAO incident, and learn defenses to prevent such exploits in real-world contracts.

Explore re-entrancy vulnerabilities in smart contracts and how to prevent them. Build a bank contract and hacker contract to demonstrate deposits and withdrawals using a balances mapping in solidity 0.8.17.

Develop and test a bank smart contract with a public remove function that withdraws funds to the caller, validating balances and updating state, and displaying total value locked.

Explore creating a hacker smart contract to exploit a reentrancy vulnerability in a bank contract, linking contracts, deploying with Solidity 0.8.17, and orchestrating deposit and withdrawal via fallback/receive logic.

Deploy a bank contract, fund it with two deposits, deploy a hacker contract, and launch a re-entrancy attack that drains all funds.

Learn to mitigate re-entrancy attacks by applying the checks-effects-interactions pattern and mutexes, using OpenZeppelin, to secure smart contracts and protect investor funds.

Explore three rug pull attack types: liquidity depth, limit sell order, and pump-and-dump schemes, and how owner privileges and backdoors in smart contracts enable fund loss, highlighting need for audits.

Explore rugpull attacks on smart contracts by examining a bank contract with an internal backdoor that lets the owner withdraw funds, and learn why code visibility matters for investors.

Explore front running in blockchain: a malicious actor monitors the mempool, pays a higher gas fee, and mines before the victim’s transaction.

Explore signature replay attacks in smart contracts and multi-sig wallets, and learn how signatures prove authorship, how replay enables unauthorized transfers, and how to prevent such exploits.

Explore liquidity pools and automated market makers powering token swaps on decentralized exchanges like Uniswap, where liquidity providers and traders earn fees.

Borrow a flash loan from a liquidity provider like Aave to perform arbitrage or yield farming within one transaction, with no collateral and automatic reversal if it fails.

Understand the audit process methodology from business requirements to manual review, using visual tools to map function interactions and assess business requirements specification for vulnerabilities in smart contracts.

Navigate the audit process through static analysis, dynamic analysis, and formal verification. Learn how static analysis flags vulnerabilities without on-chain execution, and how fuzzing and unit tests supplement verification.

Learn to conduct a smart contract audit, identify and categorize vulnerabilities by severity, and document findings, scope, and recommendations.

Audit a wallet smart contract by identifying vulnerabilities and aligning its functions with business and system requirements: receive and remove funds, check balance, and set the owner at deployment.

Examine a wallet smart contract line by line in Solidity 0.8.17, verify admin initialization, balance tracking, receive and constructor functions, and the distinction between view and payable operations.

Perform a deep manual review of smart contracts by inspecting function visibility to reveal critical vulnerabilities like access control flaws and re-entrancy risks.

Continue the manual audit to uncover vulnerabilities in withdrawal functions, add events to log sender, receiver, and value, and use blockchain explorer logs to trace transactions.

Mitigate a critical vulnerability in the withdrawal function by implementing an only admin modifier to enforce access control, ensuring only the contract owner can withdraw funds.

Practice manual review to uncover smart contract vulnerabilities, then explore a verification-as-a-service tool with static-analysis and formal verification for automated security audits.

Use a formal verification tool to find vulnerabilities in a wallet audit smart contract, learn about detection, access control, zero address validation, and viewing detailed reports.