Nessus is the world-leader in active scanners, featuring high-speed discovery, configuration auditing, asset profiling, sensitive data discovery and vulnerability analysis. A brand new reporting engine produces improved reports. Nessus can now reload its configuration file, plugins and web server while scans are in progress. The XSLT transformations now take place on the server, instead of the user’s web browser, for a smoother user-experience. The average amount of memory needed per host is now approximately 1.3 MB (versus approximately 2.8 MB previously)
Source: https://thehackernews.com/2010/11/nessus-440-new-version-release.html