Front Running

Front-running refers to the exploitative practice in which an adversary monitors pending transactions in the network's mempool and strategically submits their own transactions to gain an advantage. This typically involves the attacker issuing a competing transaction with a higher gas price or fee to ensure their transaction is prioritized and mined ahead of a victim’s transaction.

For instance, consider two transactions, Transaction A and Transaction B. Transaction B is submitted first and is pending in the mempool. An adversary, upon observing Transaction B, submits Transaction A with a higher gas price, thereby incentivizing miners to prioritize and include Transaction A in the next block before Transaction B. This manipulation allows the adversary to profit or gain advantage by executing their transaction in a more favorable position relative to the victim's transaction.

Front-running exploits the transparent and predictable nature of transaction ordering in blockchain networks, where transactions offering higher fees are typically prioritized for inclusion in blocks. This practice is particularly prevalent in decentralized finance (DeFi) applications, where transaction sequencing can significantly impact the outcome of trades, arbitrage opportunities, and other financial activities. The result is a distortion of market integrity, leading to potential financial losses for the victims and undermining the overall trust and fairness in the blockchain ecosystem.