File Hosting services offer a feature called Remote Upload. Remote Upload is a way to get files directly from remote locations and import to your file hosting account. This can be used to DDOS anyone by simply creating a program that send multiple POST request asking for a specific file (Larger files the better) and loop the requests.

I have tested this with a web radio, pointing to the radio mp3 file and the transfer was continuous which means that the file hosting service was transferring the file in the background infinitely.

Here is a list of free file hosting services that can be used as a starting point...

Download: File Hosting Linklist Vault (Full Version)
http://www.filefactory.com/file/2e9d5jl7...ion%29.rar

Note:
File Hosting Linklist Vault doesn't work with Internet Explorer. Install a Chromium based browser like Chrome or Brave - http://bit.ly/_brave_browser . (If installing Brave, keep it for 30 days to collect rewards).