Nessus scanner overview
Tenable provides an integration with IBM® QRadar® by using its Tenable.sc and Tenable.io platforms to address the needs of enterprise customers. For more information about Nessus APIs, see the A Clarfication about Nessus Professional blog by Tenable (https://www.tenable.com/blog/a-clarification-about-nessus-professional).
As of December 2018, Tenable officially removed support for Nessus APIs. As a result, Tenable does not support direct integration between Nessus and QRadar