Voice communication is an invaluable tool in our personal and business lives, but outbound roamer Caller Line Identification (CLI) spoofing is a widespread method used by fraudsters to deceive users. In this white paper, GCF’s ‘Safeguarding Future Networks and Emerging Technologies’ Knowledge Community, led by stc, offers a solutions-focused analysis of CLI spoofing’s underlying mechanisms, attack techniques, and impacts. The report proposes actionable guidelines for the telecoms industry to address current vulnerabilities and fortify networks against CLI spoofing.