Financial software, in particular software geared towards financial analysis, is widely available to the industry with many options available for use. While this won't be a make it or break it question to see if you are experienced with the program that Interactive Brokers utilizes, your interviewer will be looking to hear that you have experience on some of the available systems and that you are ready and willing to take on the challenge of learning something new if hired for this role. In the end in answering this question, make sure that you reiterate that you have the ability and the desire to learn a new program if needed to be successful in this role.