The Nessus® vulnerability scanner, is the world-leader in active scanners, featuring high speed discovery, configuration auditing, asset profiling, sensitive data discovery and vulnerability analysis of your security posture. Nessus scanners can be distributed throughout an entire enterprise, inside DMZs, and across physically separate networks. Nessus Product The Nessus Vulnerability Scanner is free to download and subscriptions for vulnerability updates from Tenable are available for two types of users: Home users and Professional Users.