How can I protect LDO NCP1117 from overheating due to short at output?
From the datasheet:-


  Features:
  
  
  Current Limit, Safe Operating and Thermal Shutdown Protection
  


If the load becomes a short circuit the regulator will limit the current. This will make it get hot, but once the internal regulator temperature reaches 175&deg;C it will shut down.    

So a short won't harm the regulator. But as the fault current could be over 1.5A some other things (PCB traces, wiring, power supply etc.) could be damaged. To protect them you could put a 'polyfuse' in series with the power input to the regulator, rated to carry the maximum expected load current.