A Flash Loan Attack in decentralized finance (DeFi) is a sophisticated form of cyberattack exploiting the unique properties of flash loans. These attacks target smart contracts responsible for issuing flash loans, a type of uncollateralized loan offered in the DeFi space. The attacker typically borrows a large sum of cryptocurrency through these smart contracts and uses it to manipulate the market or other DeFi protocols for personal gain, repaying the loan within the same transaction block.
The key to a flash loan attack lies in the permissionless and intermediary-free nature of DeFi protocols, which rely solely on smart contracts. This lack of traditional oversight makes DeFi platforms particularly vulnerable. In executing a flash loan attack, the cybercriminals leverage arbitrage opportunities or market manipulations. They may, for instance, artificially inflate or deflate asset prices, exploit protocol weaknesses, or manipulate various financial instruments within the DeFi ecosystem.
One common method involves borrowing funds to influence the price of certain assets or tokens. This manipulation can lead to artificial price inflations or crashes, allowing attackers to profit from the resultant market volatility. After completing their manipulative trades, attackers repay the loan and retain the profits, all within the same transaction block. If the attack fails, the transaction is simply reversed, as if it never happened, leaving no trace.
Several high-profile flash loan attacks have occurred, targeting platforms like dYdx, Compound, Fulcrum, and PancakeBunny. These attacks have resulted in substantial market disruptions and financial losses for the affected protocols. Due to their complex nature and the significant sums involved, flash loan attacks represent a considerable risk in the DeFi space, highlighting the need for robust security measures and vigilant monitoring of smart contract interactions.