You are not providing enough information about your case, but most likely you have been front-run.
When you are giving away free money on the blockchain, some people will take it. When you announce your request to buy some asset on Uniswap and you specify "my slippage is 100 bucks", you are giving away free money for the amount 100 bucks. If I have the asset, I can sell it to you and make profit. Is this an attack? Is it illegal for me to make profit? Obviously not.
Now, what if the person doesn't have the asset, but can buy it just before you and sell it to you? This is what front running is, and this is what happened to you. Somebody just sold you an asset they bought earlier by putting higher GasPrice on their transaction, enough higher for their transaction to be executed before yours. Since you are specifying that your slippage is 100 bucks, you're giving away an opportunity for everyone to make free money by buying this asset before you and selling it to you right after they bought it. Front-running is not an attack. Use a lower slippage and that's it.
There are many studies about front running, feed the keywords "ethereum is a dark forest" at Google and they will show up. This is the general term, but a lot have been written on the subject.
- The bot is monitoring my etherscan account ?
They are monitoring transaction pool and check PENDING transactions of everyone.
- Is it possible to counter them
no, because they are not doing anything bad, everybody makes money on something. If you don't like being front-run all the time, don't give away a lot of free money to the blockchain.