How to use Index of google search for finding ftp

For finding ftp sites you can use this trick. This is simple trick using google search engine. If you know google searching tactics,then you can whatever faster.

How to Use index of for ftp?
Search in google as
index of ftp/ +file_extensionreplace the file_extension with file extension which you want to search. (avi,mp3,aac,pdf...etc)



For Eg:
if you want to search for pdf ,then search as