Give a person a specific task in a specific environment, and stand over them, and generally all you see is that they can bumble through something pretty unfamiliar under a high degree of stress and social pressure. This is a useful skill approximately 0% of the time in a real job. Or if it is a useful skill in the job, your team has more fundamental problems than hiring to worry about!
Give them a problem to solve. Full stop. Let them take their time, do it at home before the interview perhaps, or in a quiet room on their own with their own laptop, or whatever tools they want, internet access etc, with no real time limit. If they 'cheat', you'll know because when you discuss their solution in depth later it'll be clear as day. This will test what you're really after, their ability to solve problems - allowing tools, the web, whatever else to work for them and not be arbitrary hurdles to jump over under pressure.