Users with a Nessus Professional license can configure the scanner to automatically download these plugins directly from Tenable via the internet.
Sometimes a new plugin breaks a critical scan (false positives). You can "pin" an older plugin version: Nessus Plugins Download
This is the standard commercial feed used by security consultants, auditors, and internal security teams. It provides the full suite of plugins, including: Users with a Nessus Professional license can configure