Stop paying the ransom
Like negotiating with terrorists, ransomware would cease to exist if people didn't pay the ransom. Criminals do it only because it's profitable and requires little to no effort to extort money. Even if only one in 1000 victims pay it's still a cash-cow that runs by itself.
People pay because it's an easy fix. Just hand over a few hundred dollars and all your data magically reappears. They still won't learn a proper backup routine and it will all get encrypted again as soon as they click on another "Your package has been delivered" email.
Biting the hand that feeds IT
