Susan Hennessey focuses her practice on national security, technology and defense-related matters.

Ms. Hennessey advises companies on complex investigations, law enforcement and intelligence legal processes, cybersecurity, data privacy, emerging technology regulation, and foreign investment review. Drawing on her practical experience in national security law and background as a prominent public commentator and thought leader, she helps clients navigate crises with national security dimensions, including internal investigations, congressional oversight and hearings, and sensitive media inquiries. Ms. Hennessey brings extensive experience coordinating multi-disciplinary national security crisis responses — combining strategic messaging, internal governance measures, and litigation strategies.

Prior to joining the firm, Ms. Hennessey served as Chief Counsel to the Assistant Attorney General for National Security and Chief of Staff of DOJ's National Security Division. In these roles, she managed the Division's public engagement, media response, and congressional affairs. As the principal counsel to the Assistant Attorney General, she advised on sensitive investigations and policy matters spanning terrorism, counterintelligence, economic espionage, sanctions and export control enforcement, malicious cyber activity, and foreign influence operations.

Ms. Hennessey served as the Director of National Intelligence's representative on the 2022 Senior Steering Group examining the relationship between the National Security Agency and US Cyber Command. She began her legal career as an attorney in the Office of General Counsel at the NSA.

Before joining the Justice Department, Ms. Hennessey was a Senior Fellow of Governance Studies at the Brookings Institution, where she published influential legal and policy analysis on topics including surveillance law, cybersecurity, and emerging technologies and served as Executive Editor of Lawfare. As a Brookings scholar, she provided nonpartisan expert advice, briefings, and testimony to Congress, senior government officials, non-governmental organizations, business leaders, and other stakeholders.

Ms. Hennessey is the co-author of a book on the US presidency and has contributed to several other books and monographs, including the first edition of the PLI treatise, “Cybersecurity: A Practical Guide to the Law of Cyber Risk.” Her work has appeared in the Washington Post, New York Times, Financial Times, Foreign Affairs, The Atlantic, and other leading publications. From 2017 to 2021, Ms. Hennessey appeared as a national security and legal analyst on CNN.