Tenable Network Security, Inc., the leader in real-time vulnerability management, celebrates the 15th anniversary of Nessus, the world’s most widely deployed vulnerability scanner. With more than 17,000 customers in over 140 countries, the world’s largest organizations, including the entire U.S. Department of Defense, Merck, Morgan Stanley, and Verizon, use Nessus to scan defense systems, power and utility plant control systems, healthcare information systems, and financial services infrastructures.