WARNING LINUX USERS ! If you plan to scan your local host with Nessus under Linux, then only use the Nmap TCP connect scanner. There is a bug in the libpcap which prevents Nessus from doing correct port scans, and since Nessus relies on the port scan, then you should use this one. Summary when scanning the local host : - Select 'Nmap TCP connect scan' - De-select all the others scanners (including the UDP scanner)