Connecting with sys user with Or without pwd

As we know "SYS" & "SYSDBA" is superuser privilege in oracle database.There is two method to connect SYSDBA user.
1. WITH PASSWORD2. WITHOUT PASSWORDFor example:SQL> CONN / AS SYSDBA ---without passwordFor without password need follow thing to be done.
1. Oracle Database User must have SYSDBA privileges.2. Operating System User must add in DBA group.On windows: ORA_DBA group On linux: DBA group3. In sqlnet.ora file must content "NTS" in below lineSQLNET.AUTHENTICATION_SERVICES=(NTS)For example:SQL> CONN SYS/PWD AS SYSDBA --- with password or prevent to connect without password.
1. Remove OS user from DBA group2. Edit sqlnet.ora file and change "NONE" to "NTS" in below lineSQLNET.AUTHENTICATION_SERVICES=(NONE)Default Value is NTS when sqlnet.ora file created.