This module is part of a security suite of module to improve Drupal 6.x

menu_access
Provides global and menu specific security permissions by role and user account.
- Global security for all menus (default)
- Per menu security

menu_item_access
Provides global and menu item specific security permissions by role and user account.
- Inherits security from the parent menu
- Global security for all menu items (default)
- Per menu item security