Back-Running

Back-Running is a strategy where a searcher observes a transaction that has already been executed or is about to be executed and places their own transaction immediately after it. This is typically used to capture arbitrage opportunities created by the first transaction's impact on the market price.

Unlike front-running, back-running does not necessarily harm the original trader's execution, as the victim's trade is already finalized. However, it is still a form of value extraction that captures profits that might otherwise have been available to other participants.

Back-running is often considered less predatory than front-running, but it remains a significant driver of MEV. Searchers use complex bots to scan the mempool for profitable sequences, demonstrating the high level of competition in modern blockchain markets.