Mariana Kiefer is a lawyer. She has worked for eighteen years in the Judiciary and the Public Prosecutor's Office in her country and has specialized in the field of criminal law through various postgraduate studies. She was awarded a Fulbright scholarship and attended Columbia University's Law School, where she earned her Master Degree in Law and a recognition as a Harlan Fiske Stone Scholar. She was also awarded by The Parker School of Foreign and Comparative Law with The Parker Certificate for Achievement in International and Comparative Law. Over a decade, Mariana worked in Argentina’s first Prosecution Office specialized in Computer Crime. Before joining the UN, she also gave courses and conferences on cybercrime and digital evidence for graduate students, officials, judges, attorneys, and prosecutors from various parts of the country and Latin America, collaborating with the schools of law of different universities as a lecturer, as well as writing in law journals, for instance, about digital evidence and the procedural challenges it presents.

Mariana has worked for five years in UNODC's Global Programme on Cybercrime. She serves as Cybercrime Regional Coordinator for South America. She performed her duties in Lima, Peru, during 2021 and 2022. In 2023, she moved to Montevideo, Uruguay, opening the first UNODC Programme Office in the country, where she also serves as Head of UNODC Programme Office in Uruguay.