Intro Nessus is a proprietary vulnerability scanner developed by Tenable, Inc. This blog is about the installation of Nessus Essentials on Linux. Installation Register First lets register in Tenable Nessus Essentials to get the activation code. Tenable Nessus Essentials Enter your information in the register form shown above, click Get Started. Download Nessus Mail with Activation Code We should have received a mail with Activation Code. Note down the activation code and click the Download Nessus for the downloading page.