In plain language
In blockchain vocabulary, back-running means trying to place a transaction immediately after a target transaction or event that changes a protocol's price, reserves, or state.
Where the advantage comes from
The following transaction may attempt DEX arbitrage, liquidation, or use of a newly changed price. Value comes from block ordering and the state created by the previous transaction, not merely from a gap of a few seconds.
Data required
Reconstruction needs transaction hashes, block index, contract calls, token flow, state before and after, bundles, and proposer payments when available. Two consecutive trades on a chart are insufficient to establish a backrun.
What it does not prove
Trading after a public transaction does not automatically prove abuse, manipulation, or illegality. Arbitrage and liquidations can perform functions anticipated by protocols; effects on users, control of ordering, and legal characterization require separate analysis.
Sources
- BIS, Miners as intermediaries — appendix — Defines back-running as placing a transaction immediately after another and gives operational examples.
- Ethereum.org, Maximal extractable value (MEV) — Explains inclusion, exclusion, and reordering of transactions, arbitrage, and liquidations in MEV.
- Ethereum Improvement Proposals, EIP-8209: Commit-Reveal Transaction Frames — Frames front-running, back-running, and other risks from exposing transactions before ordering.
Links
Front-running · MEV · Slippage