Interactive Brokers is the world's worst online brokerage. Their business model is to lock you out of your account so that you can't access your money.
First, they force you to select a username according some stupid and pointless rules. The reason they do this is because they want you to forget your username. And then once you have forgotten your username, it is almost impossible to recover it. They removed the feature to send your username by email, and they are now forcing you to call customer service, which from what I read it takes very long to get to speak to someone. The purpose of this is not to keep out hackers, but to keep out you.
It doesn't matter how low their interest rates are - a company with this business model cannot be trusted.