It is quite normal for top families to be very cautious here (for obvious reasons) and you would be bound by strict confidentiality clauses if you end up working for them.
The scam element could certainly come from the recruitment company - normally in the form of an advance fee scam.
They would ask you to pay for tickets, visa processing fees etc. - through their approved travel & visa agents.
They would promise that these fees & expenses would be refunded once you arrive in the UAE.
If the job is genuine - you would receive air tickets, travel accommodation to come for an interview - without you needing to pay for anything.
The acid test is therefore whether you are asked to pay any advance fees!