The foundation of Tenable is inextricably linked to the creation of Nessus, one of the most celebrated security software tools in computer history. In 1998, French software engineer Renaud Deraison created the Nessus vulnerability scanner as an open-source project to provide the internet community with an automated, free utility to audit network security configurations. Nessus rapidly achieved viral international adoption among network administrators and penetration testers. In 2002, Deraison joined forces with Ron Gula (a former NSA computer security researcher and founder of Network Security Wizards) and Jack Huffard to incorporate Tenable Network Security in Columbia, Maryland. The founders recognized that enterprise networks were growing exponentially in complexity, requiring a centralized management platform to aggregate vulnerability data across thousands of distributed Nessus scanners. In 2005, Tenable made the strategic decision to transition Nessus from an open-source model to a proprietary commercial software license, fueling rapid enterprise revenue growth. In January 2017, the board recruited Amit Yoran, the former President of RSA Security and founding director of US-CERT, as Chief Executive Officer. Under Yoran's guidance, Tenable completed a successful Initial Public Offering on the NASDAQ stock exchange in July 2018 (ticker: TENB), raising $288 million. Tenable subsequently executed landmark strategic acquisitions, including Indegy (2019) for operational technology security, Alsid (2021) for Active Directory defense, and Ermetic (2023) for cloud infrastructure entitlement management (CIEM).