How to protect against port scanners?

Is it possible to prevent nmap from observing my machine entirely? After dropping all incoming connections with iptables port scans return as "filtered". **It'd prefer if nmap couldn't see what ports existed at all**. Is this possible? The below solutions don't seem to work: http://sharadchhetri.com/2013/06/15/how-to-protect-from-port-scanning-and-smurf-attack-in-linux-server-by-iptables/ https://dangertux.wordpress.com/2011/09/18/defeating-port-scans-using-iptables/ http://prithak.blogspot.de/2011/12/blocking-nmap-scans-with-pf-and.html If it's not possible to keep nmap from seeing my device, would it be possible to rate-limit so that nmap takes a REALLY long time to fully scan my IP?