DeFi Attacks

// Flash loans allow borrowing without collateral
// Must repay in same transaction

interface IFlashLender {
    function flashLoan(uint256 amount) external;
}

contract FlashLoanAttacker {
    function attack() external {
        // 1. Borrow massive amount
        lender.flashLoan(1000000 ether);
        
        // 2. Manipulate price oracle
        // - Swap on DEX to move price
        // - Read manipulated oracle price
        
        // 3. Exploit protocol using bad price
        // - Borrow more than collateral allows
        // - Liquidate positions unfairly
        
        // 4. Profit
        
        // 5. Repay flash loan (must happen in same tx)
    }
    
    function executeOperation(uint256 amount) external {
        // Flash loan callback - execute attack here
        // ...
        // Repay loan + fee
    }
}

// VULNERABLE: Using spot price as oracle
function getPrice() public view returns (uint256) {
    // BAD: Spot price can be manipulated
    return reserve1 / reserve0;
}

// Attack pattern:
// 1. Flash loan large amount
// 2. Swap to move DEX price
// 3. Interact with protocol using bad price
// 4. Swap back
// 5. Repay flash loan, keep profit

// SECURE: Use TWAP (Time-Weighted Average Price)
// Or Chainlink oracles with multiple sources

// Real exploits:
// - bZx ($8M, 2020) - Flash loan + oracle manipulation
// - Harvest Finance ($24M, 2020) - USDC/USDT arbitrage
// - Cream Finance ($130M, 2021) - Oracle manipulation