Best way to pay contractors / not get scammed?

Hiring a contractor to do some dev work from outside the US (think India, Eastern Europe, Pakistan, etc). Historically, I have paid 50% upfront and 50% at completion but unfortunately got scammed out of the 50% upfront on a prior project when the dev did not complete what was required. Anyone have any suggestions on how to manage this (should I use a 3rd party service to handle the payment?) or other ways to structure this to minimize downside? Thanks!