What Is Sandwich Attack?

A sandwich attack is a type of MEV extraction where a bot places a buy order before and a sell order after a large pending transaction. The attacker profits from the price impact of the victim's trade. For example, a bot sees a large pending DEX swap, buys the token first (pushing the price up), lets the victim buy at a higher price, then sells immediately after for profit. Whale transactions on DEXs are common targets.