How Do They Know Where I Am?

September 27th, 2011 • 1 comment

You’re surfing the web, and without warning, some ad appears, remarkably targeted to your geographic location. How do they know? Don’t worry; it’s not that big a deal.

It’s Just Your IP Address.

Yes, that ubiquitous number – mentioned in the previous post, the IP address – is where “they” get that information. Every machine on a network (like the web) gets one: every website, every destination, every one sending or receiving I’s and O’s.  This configuration…

…amounts to some 4.6 billion possible combinations of numbers.  When you look up a website, you’re actually accessing space on one of these connected computers by means of a number like this, cross-referenced by the address you’re looking up.

Your own computer is assigned a number like this by your ISP (Internet Service Provider: cable, DSL, or dial-up service, for instance). Sometimes, they cycle their numbers, so you may or may not always get the exact same number assigned to your computer. But in all cases, it can easily be determined where your ISP is located. Sites such as demonstrate this facility.

So, who keeps tabs on where all these numbers are assigned? Google, of course. (And they give that information away for free; it’s pretty useful stuff for site analytics, for instance.)

What If I Don’t Want to Be Found?

It is possible to contract with some services to get your Internet connection to go through a proxy – a substitute IP address that looks like you’re surfing from somewhere across the globe – but really, why bother? There are a few ways we programmers can get “behind” the proxy to your actual IP address anyway. If you really don’t want to be found, you may as well change your name, move somewhere else and get out of the phone book. (Good luck with that…)

One Response to How Do They Know Where I Am?

  • 55 Communities in Delaware says:

    I like this site so much, saved to my bookmarks. “Nostalgia isn’t what it used to be.” by Peter De Vries.

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