You need to give nessus the criteria SERVER PORT LOGIN TRG RESULT as explained in more detail using the –help option. This version of Nessus is not the same as the alternative without GTK support. It looks like if you want Nessus with GTK, you’ll have to build it yourself using the ports tree. I prefer to install FreeBSD applications using pre-built packages whenever possible. I used the’make package’ option to install Nessus using the security/nessus port.”]
Source: https://taosecurity.blogspot.com/2005/06/nessus-on-freebsd-im-rebuilding-my.html