re your footnote, there was a relatively recent article[1] on 'mapping the IPv4 space' via ICMP ping, which proved it was entirely feasible, although it pales i

re your footnote, there was a relatively recent article[1] on 'mapping the IPv4 space' via ICMP ping, which proved it was entirely feasible, although it pales in comparison to the effort required for a full portscan of each host (and the benefits of a massive pool of scanning hosts to elude rate based IDS/firewalling effects) [1] http://www.securityartwork.es/2013/02/07/the-result-of-pinging-all-the-internet-ip-addresses/?lang=en http://www.securityartwork.es/2013/02/07/the-result-of-pingi... HN thread: https://news.ycombinator.com/item?id=5185160 https://news.ycombinator.com/item?id=5185160