Yesterday I saw some misinformation being distributed about IP addresses. It was in the context of a rather petty disgreement about someone’s identity on Twitter, but it did make me think that this is an area that plenty of people don’t really understand.
With that in mind, here’s a brief run-down of what an IP address is, what it says about you, and what it doesn’t. I’m by no means a networking expert, but I am an IT professional and hope that I have a decent enough grasp of the topic to explain things correctly. Please feel free to correct me if I make any mistakes.
One of these addresses (IPv4 specifically, which is the type of address that is still commonly used across the internet) is formed of four numbers, from 0 to 255, separated by dots. Every device connected to a network will have at least one of these addresses.
The more observant amongst you will have spotted a flaw in the system. If the addresses take the format 192.168.0.34, then we only have 4,228,250,625 possible addresses. That might seem like a lot, but when you think of every phone, tablet, laptop, and computer in the world, not to mention TVs, DVD players and others, it’s not very many at all.
That’s wny we have the concept of private and public IP addresses. There are ranges of addresses that are designated as “private”, which can be reused on internal networks (like your wi-fi network at home). The most common range used is 192.168.X.X
If you just had a private IP address though, you would never be able to connect to anything on the internet, just to other devices on your home network. This is where your broadband router comes in. It does the clever trick of translating your private IP address into a public one.
Your ISP (that’s BT, or Virgin Media for example) assigns a public IP address to your router, which then shares it with all the devices connected to your network. This is why an IP address isn’t quite enough to identify someone online. The public address could be shared between several people. To someone outside your own home network, they would never know who in the house is connected.
The situation becomes even more confused because of the way ISPs tend to distribute these public IP addresses to their customers’ routers. These addresses tend to be ‘dynamic’, which means that a particular public IP address isn’t tied to a particular account, let alone a particular internet user. What’s my IP address today might be yours tomorrow.
Don’t be fooled though. My IP address is assigned ‘dynamically’ by my ISP, but it has only changed once in the last three months, when I upgraded my connection speed. In that time, the router was rebooted several times, and it always ended up with the same address.
Even if your ISP does change IP addresses more frequently, it isn’t happening second by second. If you think about it, the IP address is where a web server sends its pages to, where an mail server sends its e-mails to. If that address is constantly changing, then things would fail to arrive, and need to be re-sent, all the time.
Even this dynamic changing doesn’t hide you from law enforcement, obviously. ISPs keep records of which IP address is assigned to which customer at what time. It’s this record-keeping that probably means public IP addresses change less than they might. Some ISPs also offer static public IP addresses, which are useful for users that want to be able to connect to their home network remotely.
Still, you do have a degree of anonymity from people hosting servers, who don’t have a warrant to get your account information. All they can really derive from your IP address is your (rough) geographic location (the accuracy of this varies wildly), and probably who your ISP is. If you’re connecting through a work computer, they probably have a decent idea of the company you work for, but this depends on how large the company is, and whether they have their own public IP addresses.
It’s also worth noting that public IP addresses aren’t shared across ISP customers. If they were, a web server wouldn’t know whether to send the BBC Sport homepage to you, or your neighbour. A public IP address is unique to the router in your home, at a given point in time.
In summary, your IP address isn’t some Prisoner-esque number that identifies you to all and sundry, but neither is it an unidentifable detail that gives nothing away about you.
It could, for example, be used to corrolate two online identities as the same person (or at least on the same private network). That would be a fair assumption if the IP addresses logged were the same, and there wasn’t a lot of time between the requests logged.