Oracle External Users

["Damien Lewis" <dwlewis () comcast net>]

Hello,

I'm in the process of reviewing a list of users (DBA_USERS table) from an
Oracle Database and have come across several accounts with the PASSWORD
field being "EXTERNAL".  It is my understanding that these accounts are
authenticated by the operating system, but how exactly do you go about
authenticating using this account (i.e. could I conect via SQL Plus or an
ODBC connection) and is there any other control(s) within Oracle that would
prevent any user from creating a user id that matches the account name in
DBA_USERS table on another computer and logging in as that user to the
Oracle database?

Thanks

D