Edit your /etc/ssh/sshd_config with the following changes
Set
Code:
Subsystem sftp internal-sftp
Code:
Match Group <usergroup>
ChrootDirectory /srv/www/public_html/
The directory /srv/www/public_html/ must be root owned and not writable by other users or groups (so you might want to set it to /srv/www)
Replacing the <usergroup> with the group of your new user (should be the same as your username) then restart ssh, disconnect and reconnect in filezilla.
Of course that won't stop them from accessing ssh (but it will lock them down)
Have a read of this for more information.
http://manpages.ubuntu.com/manpages/kar ... fig.5.html