SSO - limit access to internal career sites by employee type

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Hi, I have a SSO question - we have multiple internal careers sites - staff, students, adjuncts.

We have a problem, we recently noticed student workers are applying for internal staff positions.  

We import into Taleo everynight all our students and employees - so both students and employees are internals but student should only be able to access the student internal career site and regular staff should only be able to access the staff internal career site... etc..

Everyone (students and staff) are supposed to use our Portal to access Taleo - the portal will only show the appropriate career site link  based upon their role in the portal.