How to hide not-owned tables from users?

Hi all,
This may seems dummy but scenario is:
I have one schema called user1.I have created another user called user2 that I want to have select,insert,update,delete privileges on tables of user2.
Initially I granted only resource,connect to user2.Then I created and ran a script that grant select,insert,update,delete to user2.But When I query all_tables (connected by user2) I can see many more tables that are not in user_tables.
I tried to revoke access to those additional tables from PUBLIC but no chance.What should I do(revoke) to have same result from user_tables and all_tables?!
-Thanks in advance
PS: Also our .Net developers that use ODP.NET see many many more tables in list of tables.(They are connected with user2)

Dictionary table/views are managed by Oracle and automatically assign SELECT privileges to PUBLIC when Oracle is installed. You cannot do anything, but you can play with privileges to allow some group/users to run query against these views.