If you want to replicate the contents of a computer to another one over unsecure networks you can use rsync in combination with ssh to acomplish this.
rsync –delete -avze ssh firstname.lastname@example.org:/home/user/ /home/user/backupThis command will replicate the content of the remote machine to the local host. In case you want to use the other directon you can use the following command.
rsync –delete -avze ssh /home/user email@example.com:/home/user/backupIn case you need root privileges for replication take a look at pam_access.
Also take a look at the Ubuntu Wiki.