Sandwich Attack

What is Sandwich Attack?

A sandwich attack is a front-running exploit where an attacker inserts their own transactions directly before and after a victim's trade. The attacker profits by manipulating the price at the victim's expense.

How does Sandwich Attack work?

1. A user broadcasts a large token swap to the mempool.
2. The attacker buys the same token first with a higher gas fee, pushing the price up.
3. The victim's trade executes at the inflated price.
4. The attacker immediately sells at the now-higher price, capturing the spread.

Why does Sandwich Attack matter?

It costs users millions in worse execution prices annually. Every large DEX trade is a potential target, creating an invisible tax on retail traders.

Key features of Sandwich Attack

• Exploits the public mempool and predictable AMM pricing
• More profitable than simple front-running
• Disproportionately affects large trades in low-liquidity pools
• Mitigated by tight slippage limits and private mempools like Flashbots Protect

Examples of Sandwich Attack

A user swapping 1000 ETH on Uniswap could lose several percent of value to a sandwich bot. Setting slippage tolerance to 0.1 percent makes the attack unprofitable and causes the bot to skip the transaction.