Understanding Cybersecurity of Mobile Networks Act This bill requires the National Telecommunications and Information Administration to examine and report on the cybersecurity of mobile service networks and the vulnerability of such networks and mobile devices to cyberattacks and surveillance conducted by adversaries. Such report shall include (1) an assessment of the degree to which providers of mobile service have addressed certain cybersecurity vulnerabilities; (2) a discussion of the degree to which such providers have implemented cybersecurity best practices and risk assessment frameworks; and (3) an estimate of the prevalence and efficacy of encryption and authentication algorithms and techniques used in mobile service and communications equipment, mobile devices, and mobile operating systems and software.