I don’t use ftp, but wordpress comes with this nice feature to upgrade plugins automatically from the web admin interface that needs ftp.
the problem is I don’t want to enable the ftp service and make it available to the rest of the world just for that.
So I needs the following two options in proftpd.conf:
DefaultAddress 127.0.0.1
SocketBindTight on
Now restart proftpd and you’re done.