I am using Sitecore V8 + WFFM file upload control.
When user upload the file, it get stores in Sitecore Media library, and I get upload media Item Id in Custom Save action event.
So how I can:-
1.Stop uploading media file into Sitecore Media library folder.
2.Get byte array of uploaded media file so that I can pass byte data to rest service
Typically you will need to create you own 'Upload field' inherited from default wffm FileUploadField and override code responsible for handling posted files. You also might need to add custom form save action if you need to handle additionally this posted file. Also you may use idea from this post.