In plain terms. HSAR is the Department of Homeland Security's supplement to the FAR. It adds DHS-specific clauses, notably around safeguarding sensitive information and information-system security.
Who it applies to. Contractors serving DHS and its components (such as CISA, FEMA, CBP, TSA).
What it requires. Follow the FAR, then DHS additions. HSAR includes clauses (in the 3052.204-7x series) requiring contractors to protect sensitive information and meet DHS IT-security requirements, including handling of controlled unclassified information.
Why it matters. DHS contracts often involve sensitive homeland-security data, so its safeguarding clauses carry real compliance and reporting weight.
Citation. HSAR, the Homeland Security Acquisition Regulation supplement to the Federal Acquisition Regulation (FAR), codified in the FAR System at Title 48 of the C.F.R.