As I said: * Read what others write about the broker, cut the outliers out and take the rest as a fair representation * Check how long the broker has been in business; lawsuits; settlements; violations; official complaints;... * Check what people say about withdrawals, conflict resolutions, customer service... It's not that hard but you gotta do your due diligence. IB is one of the best if not the best and safest broker among those who take on retail accounts.
If you are a Hedge Fund and you want to buy 100,000 shares of say AMZN stock and split this in chunks of 1,000 shares orders (Total of 100 orders), every separate order will have a unique ID. The broker still cannot front run, because he is obliged to execute the client order first. So it goes like this: HF sends first 1,000 shares buy --> Broker executes them first --> Then Broker buys for his clients (Using his POA) HF sends second 1,000 shares buy --> Broker executes them first --> Then Broker buys for his clients (Using his POA), And so on. Now you are referring that after a couple of buy order chunks, the broker now knows that you are buying, so he effectively knows what you are up to or your positional direction and this is what you are referring to that he can still do some sort of middle running while the Hedge Fund is scaling/slicing their order. Now this is true and an old tactic which used to happen a lot by floor traders back in the days and Hedge Funds and Large Traders got note & implement various tactics to hide their intentions from their brokers or the floor traders. First they use multiple brokers and spread the orders among them, not only this, but they might also buy, then sell, then buy, then sell and go short, then cover, then short again, before they finally cover & go long. These swings (Especially when randomized without a particular pattern) make it very very difficult for the brokers to identify which side are you really trying to take.
If I have a trading account with a broker and the money is at Dorman. Who can see my orders and trades? My broker? Dorman? Or both? Does my broker place the orders directly at the CME or does it pass thru Dorman?