Miner Extractable Value (or MEV) refers to the profit that a miner can potentially make by reordering or censoring transactions on a blockchain network. This can happen because miners have the power to choose which transactions they include in the blocks they mine.

Front-running occurs when a trader's transaction is seen by another party before it is included in a block, and that party can then copy the transaction and submit their own transaction with a higher gas fee to ensure their transaction is processed first, potentially earning a profit at the expense of the original trader.

A sandwich attack is a type of front-running where a trader places a transaction, and then a malicious actor places two transactions in quick succession. The malicious actor sees the first transaction and submits two transactions that get processed, both before and after the trader's transaction, earning a profit by manipulating the market.

To protect themselves from MEV, front-running, and sandwich attacks, traders can use tools like flashbots or keep an eye on gas prices and choose to use limit orders instead of market orders to avoid slippage. When using the 0x protocol and 0x Gasless feature, traders can benefit from the smart order routing and other security measures built into the protocol, but should still be aware of the risks and take steps to protect themselves.