Nessus is a free, up-to-date, and full featured remote security scanner for Linux, BSD, Solaris and some other systems. It is multithreaded, plugin-based, has a nice GTK interface, and currently performs over 330 remote security checks. It has powerful reporting capabilities (HTML, LaTeX, ASCII text) and not only points out problems, but suggests a solution for each of them.
79cdda12e97a24654cf84e69ddd8b1697419d0b23954e53e02c7e3bda376b12c