It depends on which task
If it is a common task, like wires, card swipe, or insert keys.
Common tasks are either everybody has it or nobody has it. If someone does card swipe and you don't have it, they are faking.
With a download, you just have to count to nine.
If it takes them less than nine seconds they are faking.
If you see someone doing trash in cafe and/or o2, at the next meeting say they have trash, if they say they don't that means they were faking.
The task bar can sometimes work, but it's very unreliable.