You can restrict access to selected recruitments for selected groups of users, (e.g., external recruiters) so that they can only see recruitments they have been assigned to.
Go to Settings -> Permissions, hover above the red circle at the bottom right and select Add new group. Next, give it a name and click Save:
Then, click its name on the list to edit its permission settings, expand Restrictions at the very bottom, and click the box next to Access only to your recruitments:
The changes will be saved automatically. In the same manner, you can restrict access to recruitments to an existing group – simply go to Settings -> Permissions, select a group from the list on the right and go to Restrictions at the very bottom.