lpress writes "All botnets are evil, right? Not Carna. It crawled the Internet ethically without doing harm and gathered a ton of interesting data. For example, Carna counted pingable IP addresses, those behind firewalls and those with reverse DNS records, for a total of 1.3 IP addresses in use. The anonymous author has also posted a description of the Carna methodology and results. There are also maps and dynamic graphics and all the data is available for download."