How do IP addresses work? That’s a good question. The simple answer: they work just about like a street address. Say your computer has the IP address 184.108.40.206, that’s the address he “lives” on.
But there’s a much longer answer: of course, your computer’s IP address can change, for example, if you have a dialup internet connection and provider assigns you a new IP address every time you connect.
However, the IP addresses themselves never change as they are pulled from a fixed address pool. Many addresses are owned by corporations and providers so they’ll never change hands unless the company sells them off. This happens occasionally since only about 4 billion IPv4 addresses are available and that pool has already been exhausted. There are IPv6 addresses too which have a different format and are available in almost unlimited quantities.
Anyway, an IP address – IPv4 or IPv6 – will never go away. It may be reassigned, but it’ll never vanish from the address pool. Also, it’s pretty much known who owns which IP address – you can’t buy address blocks without identification anyway. Your computer merely gets assigned a number from your provider’s pool, and the provider knows exactly who got which address. Maybe not forever, but usually for a few days after the assignment. That’s what today’s anti-terror laws can do to your privacy.
So why is dialogue like this still a thing in 2017? This is from Audience’s show Rogue, episode 4×2:
Police Tech Guy:
The e-mail to the nurses, they weren’t sent from the Nursing Agency.
They were, however, sent from the same IP address. Bad news.
That address has been burned.
I’m not even sure what he means exactly. Does he say each of the e-mails were sent by the same IP address, which however is different from the one the nursing agency uses? Or does he claim the mails were sent using the nursing agency’s IP address? And what does he mean by “burned”? Is the provider unable to tell him who had that IP address when the e-mails were sent? Considering the incident occurred just a day ago, I find that hard to believe.
And if it was indeed the agency’s IP address we’re talking about, it’s pretty clear who owned it, isn’t it? Of course, that doesn’t help the investigation at all, but unless the agency got hacked it must have been someone inside the company.
And to think they would have gotten away with it by having him say “We have no idea who sent them.” But that wouldn’t have sounded as flashy as “burned”. Because everyone knows “burner phone” and thinks everything else in the world works just like that.