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Market Abuse Traditional Finance

Front-Running

Executing orders on a security ahead of a large pending order that will predictably move the price.

1 Introduction

Front-running occurs when a broker, trader, or other market participant executes orders on a security ahead of a large pending client order that they know will predictably move the price. By trading first, the front-runner captures a risk-free profit at the client's expense. In DeFi, front-running is automated via MEV (Maximal Extractable Value) bots that reorder blockchain transactions for profit.

$1.4B

MEV extracted on Ethereum (2021-2023)

0.3-2%

Typical per-trade cost to victims

~12 sec

Ethereum block time (MEV window)

2 Front-Running Sequence - Interactive Timeline

$500K

Front-Runner Profit

$0

Client Overpay

$0

Price Slippage

0%

3 Detailed Analysis

TradFi vs. DeFi Front-Running

Traditional Finance

A broker sees a pending client order for 500K shares and buys ahead of it. Regulated under MiFID II best execution obligations and SEC Rule 17a-3/4.

DeFi / MEV

MEV bots monitor the mempool for pending DEX transactions. They submit their own transaction with higher gas fees to be included first in the block (sandwich attacks).

The Sandwich Attack (DeFi)

The most common form of DeFi front-running. The attacker: (1) sees a large pending swap in the mempool, (2) places a buy order before it (pushing the price up), (3) lets the victim's trade execute at the inflated price, then (4) immediately sells at the higher price. The victim receives fewer tokens than expected due to the price slippage caused by the attacker.

Red Flags

  • Broker personal trades consistently placed just before large client orders
  • Systematic same-direction trades in broker's own account minutes before client execution
  • On-chain: transactions consistently included in the same block as, but before, large DEX swaps
  • Abnormally high gas fees paid to prioritize transaction ordering

Related Fraud Types

Insider Trading

Trading securities based on material, non-public information in breach of a fiduciary duty or other relationship of trust.

Spoofing & Layering

Placing and quickly canceling large orders to create a false impression of supply or demand.

Pump & Dump

Coordinated buying to inflate a token price followed by a mass sell-off, leaving late investors with losses.