How to Protect Your Trades from Sandwich Attacks (MEV Blockers)

The Invisible Tax: Why You’re Losing Money on Every Trade

I remember the first time I got “sandwiched.” I was buying a new token on Uniswap. The price looked fine. I clicked swap. The transaction went through. But when I checked my wallet, I had about $200 less than I expected. The price had jumped right as I clicked the button, then dropped immediately after.

I wasn’t unlucky. I was hunted. A bot saw my trade sitting in the “waiting room” of the blockchain and decided to take a bite out of my profit. This is the reality of trading on Ethereum today. It’s called a sandwich attack. It’s part of a bigger game called MEV, or Maximum Extractable Value.

If you use MetaMask and trade on DEXs like Uniswap, SushiSwap, or PancakeSwap, you are a target. This guide is about how to stop being the “meat” in the sandwich. I’ll show you how to hide your trades and keep your money.

Quick Summary:

• Sandwich attacks are a hidden tax on every trade you make on decentralized exchanges.
• Bots watch the public mempool to front-run your buy order and back-run your sell order.
• Using an MEV Blocker RPC is the easiest way to hide your trades from these bots.
• Slippage settings are your first line of defense, but they aren’t enough on their own.
• Platforms like CowSwap and Flashbots Protect offer “private lanes” for your transactions.

What Exactly is a Sandwich Attack?

Think of the blockchain as a public bus station. Everyone can see who is waiting for the bus. In crypto, this waiting room is called the mempool. When you send a trade, it sits in the mempool before a validator picks it up and puts it into a block.

Bots, run by “searchers,” scan this mempool 24/7. They look for large trades that will move the price of a token. When they find your trade, they do three things:

The Front-run: The bot submits a buy order for the same token you are buying. They pay a higher gas fee so their trade happens right before yours. This pushes the price up.

Your Trade: Your trade executes at the higher price the bot just created. You get fewer tokens than you wanted.

The Back-run: The bot immediately sells the tokens they just bought. Since your trade pushed the price up even further, they sell for a profit.

The bot wins. You lose. The price ends up right back where it started, but you have less crypto in your wallet. It’s a risk-free profit for the bot owner.

MEV: The Dark Forest of Ethereum

Sandwiching is just one part of MEV. MEV stands for Maximum Extractable Value. It’s the total amount of money that can be squeezed out of block production. In the old days, miners did this. Now, in the Proof of Stake era, it’s a complex dance between searchers, builders, and relayers.

I’ve spent months looking at the data. Billions of dollars have been extracted from regular users. Some call it “efficiency.” I call it a tax on the little guy. The Ethereum network is often called a “Dark Forest” because if you show any sign of value, something will jump out of the shadows to take it.

The Players in the Game

To fight back, you need to know who is in the room. There are three main groups:

Searchers: These are the guys running the bots. They look for sandwiches, liquidations, and arbitrage opportunities.

Builders: They take the transactions from searchers and regular users and package them into a block. They want the most profitable block possible.

Relayers: They act as the middleman between builders and the actual validators who secure the network.

Slippage: The Kick Me Sign on Your Back

When you trade on a DEX, you see a setting called “Slippage Tolerance.” Most people ignore it. That’s a mistake. Slippage is the maximum price change you are willing to accept to get your trade done.

If you set your slippage to 10%, you are telling the bots: “I am okay with paying 10% more than the current price.” The bots see this and will sandwich you until you hit that exact 10% limit. They take every penny of that “tolerance” you offered.

Pro Tip: Never use “Auto” slippage on low-liquidity tokens. I’ve seen bots drain 15-20% of a trade because the user left their slippage wide open. Keep it as low as possible, usually 0.1% or 0.5% for big tokens.

The Solution: What is an MEV Blocker?

How do you stop a bot from seeing your trade? You stop using the public mempool. This is where MEV Blockers come in. An MEV Blocker is a special “RPC endpoint” you add to your wallet.

Instead of broadcasting your trade to the whole world, an MEV Blocker sends your trade directly to a group of “trusted builders.” These builders promise not to sandwich you. They keep your trade private until it is safely tucked inside a block. If there is any “back-running” profit to be made from your trade, some blockers even kick that money back to you instead of the bot.

How to Change Your RPC (The 2-Minute Fix)

If you use MetaMask, you are likely using the default Infura RPC. This sends your trades straight into the jaws of the bots. Changing it is the single best thing you can do for your crypto security.

Step-by-Step Guide:

1. Open MetaMask and click the network selector (usually says “Ethereum Mainnet”).
2. Click “Add Network” then “Add a network manually.”
3. Enter a name like “MEV Blocker.”
4. For the RPC URL, use something like https://rpc.mevblocker.io.
5. Chain ID is 1 (for Ethereum).
6. Currency symbol is ETH.
7. Save and switch to this network.

Now, when you trade, your transaction is invisible to the public mempool. I did this last year and haven’t been sandwiched since. It’s that simple.

Top MEV Blockers Reviewed

Not all blockers are the same. Some are faster, some are more private. Here is what I’ve found from testing them.

1. Flashbots Protect

Flashbots is the gold standard. They basically invented the way we handle MEV. Flashbots Protect is their RPC. It’s reliable and used by thousands of pros. The only downside? Sometimes your trade takes a few seconds longer to land because it’s waiting for a Flashbots-aligned builder to win a block.

2. MEV-Share (by Flashbots)

This is the next level. MEV-Share doesn’t just hide your trade; it auctions off the right to “back-run” you. If a bot makes money by following your trade (which is often harmless), that bot has to pay you a “rebate.” You actually get paid to trade. I’ve seen users get $5 or $10 back on large trades.

3. CowSwap (The “Coincidence of Wants”)

CowSwap isn’t just an RPC; it’s a whole different way to trade. They use “intents.” You don’t say “I want to swap X for Y.” You say “I want Y, and I’m willing to give up X.” CowSwap then finds a “solver” to get you the best price. If two people want to trade the opposite thing at the same time, they just swap directly. No bots involved. No gas fees if the trade fails. It’s my favorite way to trade large amounts.

The “Jaredfromsubway” Factor

You can’t talk about sandwich attacks without mentioning jaredfromsubway.eth. This is a legendary bot that has made millions of dollars. At one point, this single bot was responsible for a huge chunk of all gas spent on Ethereum. It’s highly sophisticated. It targets specific tokens and uses complex math to squeeze every drop of value out of retail traders.

I looked at his wallet once. It’s a constant stream of thousands of transactions. This isn’t a hobbyist; it’s a high-frequency trading firm disguised as a wallet. If you aren’t using an MEV blocker, you are literally donating to Jared’s retirement fund.

Intent-Based Trading: The Future of Protection

The industry is moving away from “transactions” and toward “intents.” What’s the difference? A transaction is a set of instructions: “Go to this contract, call this function, pay this much gas.” An intent is a goal: “I want 1,000 USDC for my 0.5 ETH. Figure out how to do it.”

Platforms like 1inch Fusion and UniswapX use this. They take your order and let professional “fillers” compete to give you the best price. The fillers handle the gas and the MEV risk. If they get sandwiched, it’s their problem, not yours. You get the price you signed for, or the trade doesn’t happen.

Toxic Flow vs. Non-Toxic Flow

Here is something most guides won’t tell you. Builders actually want your trades. Your trades are “non-toxic flow.” This means you aren’t a high-speed bot trying to arbitrage them. You’re just a person buying a token because you like it.

Builders love non-toxic flow because it makes their blocks more valuable without the risk of being “played” by other bots. By using an MEV blocker, you are signaling that you are a “good” trader. In return, builders give you priority and protection. It’s a win-win.

The Cost of Being Lazy: Real Data

Is it really worth the effort to change your RPC? Let’s look at the numbers. In a typical month, MEV bots extract between $10 million and $50 million from Ethereum users. On a $10,000 trade, a sandwich attack can easily cost you $50 to $100. Over a year of trading, that’s thousands of dollars gone.

I’ve seen people complain about high gas fees, then turn around and lose 10x that amount to a sandwich bot without even realizing it. Gas is the fee you see. MEV is the fee you don’t. Don’t be lazy. Change your settings.

Checklist for a Safe Trade

Before you hit “Swap” on your next trade, run through this list. It will save you money.

• Check your RPC: Are you on an MEV-protected network? (Flashbots, MEV Blocker, etc.)
• Check your Slippage: Is it set to the lowest possible amount? (Start with 0.1% or 0.5%).
• Check the Liquidity: If the token has very little liquidity, even a small trade will move the price. Be careful.
• Use an Aggregator: Use 1inch or CowSwap instead of going directly to Uniswap. They often have built-in protection.
• Verify the Contract: Make sure you aren’t trading a “honeypot” token that bots use to lure you in.

Hardware Wallets and MEV

Does a Ledger or Trezor protect you from sandwich attacks? No. A hardware wallet protects your private keys. It stops people from stealing your funds. But it doesn’t change how your transaction is processed on the network. A bot doesn’t care if you signed your transaction with a piece of plastic or a browser extension. The trade looks the same in the mempool. You still need an MEV blocker RPC even if you use a hardware wallet.

The Future: Proposer-Builder Separation (PBS)

The Ethereum developers know MEV is a problem. They are working on something called Proposer-Builder Separation (PBS). The goal is to make the MEV market more transparent and fair. But PBS won’t stop sandwich attacks entirely. It just changes who gets the money. As long as there is a public mempool, there will be bots. Your best defense will always be private transaction routing.

Conclusion: Take Control of Your Trades

Crypto is hard enough without bots stealing your lunch. Sandwich attacks are a technical problem, but they have a technical solution. You don’t need to be a coder to protect yourself. You just need to stop using the default settings.

Switch your RPC to an MEV blocker. Use intent-based platforms like CowSwap. Keep your slippage tight. It takes five minutes to set up, and it will save you money every time you trade. Stop being the meat. Start being the hunter.