I think I can intercept any packet from my app and change the url, and the params such that the users’ account would de delete / other stuff could be deleted.
How do I protect against this? since the auth_token, and cookie are passed in every packet?
The standard protection agains packet sniffing is to secure your connections with HTTPS.
Here is some info:
http://collectiveidea.com/blog/archives/2010/11/29/ssl-with-rails/