As a proud U.S. Marine veteran, Brennan became involved with CREST International in 2016 while serving the Global Board of Directors for the Open Web Application Security Project (OWASP). Seeing similar goals, he became more active in the CREST organization and was nominated to lead the organization’s U.S. Advisory in 2019. Over his career, Brennan has amassed security expertise across the cybersecurity spectrum, including penetration testing, vulnerability assessment, application security, threat intelligence, and more. In addition to being CREST USA Chairman, he is the Chief Information Officer of the national law firm Mandelbaum Barrett, overseeing critical infrastructure, privacy, and security operations. He is also an Advisory Board Member of the information services advisory Gerson Lehrman Group, a Cyber Fellows Advisory Council Member, a Member of the Information Technology Advisory Committee of the County College of Morris, a Senior Advisor and Industry Advisory Board Member of the New Jersey Institute of Technology, and a Cyber Fellows Advisory Council Member of the NYU Tandon School of Engineering.