1) VoIP allows voice calls over IP networks like the internet using protocols like SIP, while UC integrates real-time services like chat and video with non real-time services like email and voicemail.
2) Common VoIP and UC threats include eavesdropping, vishing, DoS/DDoS attacks, call tampering, and man-in-the-middle attacks.
3) Securing VoIP and UC against these threats involves measures like encryption, authentication, firewalls, and policy enforcement.