sqlplus security

Hi. Is there any way to prevent users from logging in to the database using:

$ sqlplus <user>/<password>

This presents a security problem since anyone doing a ps can pick these up.

We would like people to login using:
$ sqlplus

Enter user-name: <user>
Enter password: <password>

Alternatively can sqlplus disguise it's command line arguments so no one can pick them up?

--

Bobby Mander          bum_at_hyperplane.com
Hyperplane, Inc.      bmander_at_att.net
                      http://home.att.net/~bmander/