Unlike traditional web applications where the server is a black box, Web3 applications expose their entire backend logic on the blockchain. This transparency creates a unique and perilous attack surface.
| Feature | Web2 (Traditional) | Web3 (DApp) |
|---|---|---|
| Backend Logic | Hidden on private servers | Public smart contracts (Bytecode) |
| Data Storage | Centralized Database (SQL/NoSQL) | Distributed Ledger (Blockchain/IPFS) |
| Identity | Username/Password | Private Key / Wallet Signature |
| Trust | Trust the Company | "Trustless" (Verify the Code) |
A Decentralized Application is composed of three distinct layers, each with its own vulnerabilities.
The React/JS interface users see. Vulnerable to traditional XSS, phishing (fake contract addresses), and dependency supply chain attacks.
The Smart Contract logic. Once deployed, it is immutable. Vulnerabilities here (Reentrancy, Overflow) are permanent unless upgrade patterns are used.
The user creates the transaction. Risks include unlimited token approvals, blind signing, and private key theft via malware.
In Web3, attackers don't need to steal credit card numbers and sell them on the dark web. They attack the protocol directly to drain liquidity. The path to profit is immediate and often anonymous (via Mixers).
Common Pattern: Attackers monitor the "Mempool" (pending transactions). If they see a profitable transaction, they can "Front-run" it by paying a higher gas fee to execute their transaction first.
Billions have been lost not because of cryptography failures, but because of implementation errors and "Centralization Risks".
Many "Decentralized" projects actually have a single Admin Key that can upgrade contracts or pause withdrawals. If this key is stolen, the project is dead.
Defi protocols relying on a single source for price data (e.g., a Uniswap pool) can be manipulated using Flash Loans to crash the price and liquidate users.