user access of news groups with out authentication

[sidharth]

hi,
  is it possible to define user wise access to the
newsgroups

For eg i want a user to access a particular news group
and another user not able to see, post in that group
with user authentication

or there is some way so that i can tell reader.conf to
read a particular file to list the users for a
particular news group access

any help is appreciated
regards
sid's

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