_bj1v

Not quite. My method was far from what this guy is doing. I only did a minimal ping, one packet per IP with a Python script:

  s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.getprotobyname("icmp"))
  for address in addresses:
    s.sendto(pkt, (address, 1))
  s.close()

At the same time, I had tcpdump running, i.e. "tcpdump -i en1 icmp[icmptype] == icmp-echoreply" to capture the replies.

Thanks for the list of 1.3 billion potentially in-use IP addresses! I had to spend USD15 to run 8 medium EC2 instances for 16 hours to only find 200++ million hosts.