Nessus is one of the granddaddies of vulnerability scanners. Today, Nessus is not only a powerful open source product in its own right, it is the basis for some of the most powerful commercial vulnerability scanners available. We reviewed Nessus in order to assess the current state of the product. What we found was that Nessus in its Linux incarnation is, largely, a powerful scan engine. It works most effectively in the company of other products, such as the Tenable Security Center.