SimpleSwap

MEV & Sandwich Attacks: How Bots Skim On-Chain Trades

A sandwich attack happens when a searcher places one trade before a DEX swap and another after it, profiting from the price movement caused by the user's trade.

How a sandwich attack works

Searcher front-runs
Your swap executes
Searcher back-runs

The first trade moves the price before your swap executes. Your transaction then pushes the price further, letting the searcher trade again immediately after and capture the difference. Your swap sits between the two trades – hence “sandwich.”

Sandwiching is not a scam in the same sense as phishing or impersonation: it relies on transaction ordering and market mechanics rather than deceiving you into sending funds.

A related scam is different: fake “MEV bot” tutorials or contracts promise easy trading profits, then ask you to fund a contract designed to send your crypto to the scammer.

Every transaction involved is technically valid. That is exactly what makes it hard to regulate – and easy to underestimate.

$60M

estimated annual trader losses to sandwich attacks on Ethereum

70%

of measured attacks trace back to a single operator

~40%

of attacks target “safe-feeling” stablecoin and low-volatility pools

What to watch for

  • Wide slippage settings – more room between your expected and accepted price means more room to extract.
  • Large trades in shallow liquidity – the bigger the price impact, the more attractive the trade is to a searcher.
  • “Easy MEV profit” offers – be suspicious of tutorials or contracts promising passive returns after you fund them.

What actually reduces exposure

Ranked roughly by how much they help.

  1. 1

    Use a private transaction relay

    Services like Flashbots Protect route your trade to block builders without it passing through the public mempool, so searchers cannot see it coming.

  2. 2

    Set slippage tolerance deliberately

    Your slippage setting is the ceiling on how much a sandwich can take. A wide default on a large trade is an invitation.

  3. 3

    Split large orders, trade deeper pools

    Sandwich profit scales with how much your trade moves the pool – smaller orders and deeper liquidity leave less to extract.

MEV-protected or private transaction routing and more deliberate slippage settings can reduce exposure, but they are not an absolute guarantee.

Want to see what happens behind the trade?

The full guide explains mempools, slippage, private transaction routing, real sandwich attacks and how fake “MEV bot” schemes turn the same concept into a scam.

Key takeaways

  • A sandwich attack relies on transaction ordering, not deception – every transaction involved is technically valid.
  • MEV-protected routing and tighter slippage reduce exposure, but neither is an absolute guarantee.
  • This isn't a scam in the phishing sense, but the loss is real and worth understanding before you trade.

MEV & Sandwich Attacks FAQ

A bot spots your pending DEX trade in the public mempool, buys the same asset just before you to push the price up, lets your trade execute at that worse price, then sells immediately after. Its profit is calculated from what you received.

Usually, you do not – the core problem. Your transaction succeeds normally with no visible error. Block explorers such as EigenPhi let you inspect a transaction and see whether it was bracketed by trades from the same address in the same block.

No. Nearly 40% of measured attacks targeted low-volatility pools. The attack exploits transaction ordering, not price volatility, so “it's just a stablecoin” does not protect you.

A standard SimpleSwap exchange does not broadcast a signed DEX trade with your slippage tolerance attached, which is what searchers hunt for in the public mempool. You send an ordinary transfer to a deposit address, and routing happens on the provider's side afterward. That is a structural property of the flow, not a guarantee – and it does nothing for trades you make directly on a DEX.

No, but the confusion here is usually about fake “MEV bot” schemes that borrow real MEV terminology to sound credible. SimpleSwap is a self-custodial swap service operating since 2018 with no connection to bot-deposit schemes promising guaranteed sandwich-attack profits – if something asks you to fund a “bot” first, that's the scam, not SimpleSwap.