Comment by jcynix

Back of the envelope calculation: there are 2^32 possible IPv4 addresses, you can easily ping about 1K addresses in parallel[1] on a standard linux machine and there are 86,400 seconds in a day. So after about 50 days you tried all possible IPv4 addresses. Now set up a farm with more than 50 machines ... e.g. as a state owned actor (or a "private" bot farm) and you'll learn about newly connected machines within hours.

[1] Did actually use 1K threads to do parallel TCP connections more than 20 years ago already, so 1K is an easily reachable lower limit nowadays. You'll need an ISP which allows that to be done ... or a distributed bot farm.

Edit: spelling