Speigel Online has an interesting story about how a Hacker Measures the Internet Illegally with Carna Botnet. The anonymous hacker(s) exploited unprotected devices online to create a botnet with which they then used to take a census of those online.
So what were the actual results of the Internet census? How many IP addresses were there in 2012? “That depends on how you count,” the hacker writes. Some 450 million were “in use and reachable” during his scans. Then there were the firewalled IPs and those with reverse DNS records (which means there are domain names associated with them). In total, this equalled some 1.3 billion IP addresses in use.