Recently, I’ve been studying an interesting blockchain phenomenon—I’d like to talk with everyone about MEV bots and sandwich attacks.

First, let’s talk about what MEV is. Simply put, MEV (Miner Extractable Value) is the value that miners can extract on the blockchain. Put bluntly, it’s about profiting by adjusting the order of transactions. There’s a person called jaredfromsubway.eth—his MEV bot is said to have executed more than 230,000 transactions, affecting more than 100,000 victims. You could say he’s one of the most successful bot operators in the world.

You might think, doesn’t this sound like they’re doing something bad? Actually, an MEV bot is like a kitchen knife—it depends on how it’s used. In traditional stock markets, high-frequency trading firms using front-running strategies have long made it standard practice, and no one thinks that’s unreasonable. DeFi is pretty much the same.

So how do MEV bots specifically “attack”? The most common method is sandwich attacks. The principle of this kind of attack is: the bot monitors your transaction, then inserts its own trades before and after yours, thereby profiting from it. It sounds pretty sneaky, but that’s also why some people see it as a plague in DeFi.

From a bad perspective, sandwich attacks do indeed exploit retail investors who don’t understand blockchain very well. For example, someone might set an extremely high slippage (sometimes even 99%) just to get a new token purchase through—then they end up becoming a target for MEV bots. But from the standpoint of economic efficiency, this mechanism actually also helps the market find a balance, bringing prices closer to the real relationship between supply and demand. So this isn’t purely a black-and-white issue.

Can you avoid sandwich attacks? To be honest, you basically can’t. As long as there’s profit to be made, someone will run an MEV bot. This is an inevitability of the market—just like front-running in stock trading, it’s deeply ingrained.

That said, new countermeasures have emerged recently. FlashBots is a tool designed to hide your transactions, so that MEV bots can’t find you. Now, you could say that MEV bots and FlashBots are engaged in a continuous “arms race.”

Overall, understanding the logic behind MEV bots and sandwich attacks is important. This isn’t just a technical issue—it reflects market structure. Whether you’re a trader or an observer, it’s worth spending time to understand these underlying dynamics.