The “user segment” encompasses end users and their equipment that interact with mission services, SATCOM terminals, customer ground gateways, tasking portals, and downstream processing pipelines for delivered data. Where these environments interconnect with mission cores, a compromised user domain becomes a springboard. Attackers can inject malformed tasking requests that propagate into payload scheduling, craft user-plane messages that traverse gateways into control or management planes, or seed data products that flow back to mission processing systems and automation. In broadband constellations and hosted services, user terminals may share infrastructure with TT&C or provider management networks, creating opportunities to pivot from customer equipment into provider-run nodes that the spacecraft trusts.