From version 1.0.172, WFilter free is able to block dropbox on network. In this guide, I will demonstrate you to block dropbox with WFilter free edition.
1.Download dropbox protocol

2.New a “block dropbox” policy
New a “block dropbox” policy in “Policy Settings”->”Blocking Level Settings”.

3.Define ip ranges to be blocked
Apply the “block utorrent” policy to client ip ranges in “User-device List”.

4.Check dropbox program and website
Can’t connect to dropbox server and website.

