We first start with the Nessus scan results for our Ubuntu server host:

Unsurprisingly, we just find a bunch of information vulnerabilities, since there are just two services installed—FTP and SSH. The FTP server has a backdoor baked into it; however, it has not come out as a critical vulnerability. If you look at the last result in the Linux scan, it does detect that vsftpd 2.3.4 is installed, which comes with a backdoor.

To summarize the other results on this page, the Nessus SYN scanner simply lists a number of services enabled on the host:

There is a bunch of more useful information on this page that can be manually inspected. As of now, we shall focus on exploitation of the vsftpd service that we installed on the Ubuntu server.