Frontrunning (Blockchain)
Also known as: Transaction Front-Running, Mempool Sniping, DeFi Exploit
A malicious strategy where attackers exploit transaction ordering to gain unfair financial advantage.
Frontrunning in blockchain refers to the act of observing a pending transaction in the mempool and submitting a similar transaction with higher gas fees to ensure it is processed first. This exploitative tactic is commonly used in decentralized finance (DeFi), especially on automated market makers (AMMs), where attackers anticipate price movements caused by large trades. Frontrunning undermines fairness, causes slippage, and can lead to MEV (Maximal Extractable Value) extraction. Protocols are developing mitigations such as private transaction relays, batch auctions, and encrypted mempools to counteract frontrunning behavior.