how to hide the tabs in top link bar from unauthorized users.

Question

In SharePoint foundation not support Audience concept.
then how to hide the tabs in top link bar from unauthorized users.
that means i have site collection is there in that District site and Department site.
here when Admin enter into the main portal he able to view the District site and Depatment site and remaining links.
when District user enter into the portal he not able to view the Department site-------is it possible.
in the same way Department user enter into the portal he not able to view the District site-----is it possible.
please give me reply.

Thank you..........