How DO they do it?

December 15, 2007 10:24 PM

How do those internet ads that reference your hometown (or a reasonable facsimile) get that information and use it? Furthermore, is there any way to stop it?

I just ran across an ad trying to push car insurance in the town next to mine. Over the years, I've seen many ads like this, whether they're for car insurance, dating (the most likely culprit), or any number of other things. What are these sites using to find out what town I'm in? I suspect it's my IP address, but I'd love to know for sure.

Also, is there a way to stop them from getting that information and using it to try to push their wares? I'm not expecting there to be, and that's completely fine, but if it can be blocked, then why not?

posted by phaded to computers & internet (15 comments total)

There are services which try to map IP addresses back to geographic regions, and so I assume that that's what those targeted ads are using.

You can avoid it by routing your request through a proxy — either at the application level (HTTP proxy, Tor, etc.) or the packet level (using a VPN connection to some geographically distant network). There isn't really any other way to hide your IP address.
posted by hattifattener at 10:28 PM on December 15, 2007

They don't actually know where you live, they're just guessing based off information linked to the IP address you've been assigned, and this is usually limited to City/State. You don't need to worry.
posted by bizwank at 10:34 PM on December 15, 2007

it's also possible that they've figured out how to read cookies from well known sites like amazon that store that kind of data.
posted by cosmicbandito at 10:40 PM on December 15, 2007

It's GeoTargeting based on your IP address. The only way to conceal your IP address is by using a web proxy, but I don't think that's worthwhile just to avoid targeted ads.
posted by justkevin at 10:47 PM on December 15, 2007

yep, Don't worry about it... there are dozens of ways to determine that your IP address belongs to a certain geographical region. Any website or ad server can know approximately where you live (City/State type of info).
posted by zengargoyle at 10:48 PM on December 15, 2007

As already mentioned above, they really have no idea who you are - they are just matching up your IP address with a database.

The GF and I have a good laugh over the dating ones - we live in a very small town, and they usually pull up the names of the smaller towns - or even intersections - that surround us.
posted by davey_darling at 10:48 PM on December 15, 2007

Your IP address is linked to your geographical location through your IP provider, which of course you could spoof and change etc. Anyway, try this site for some fun.
posted by caddis at 10:54 PM on December 15, 2007

cosmicbandito, my amazon cookies contain no such information, nor do any of my other thousands of cookies. unless you mean they're somehow swiping cookies and then retrieving their personal data from amazon's servers, in which case seeing geographically targeted ads is the least of their worries.
posted by bizwank at 10:55 PM on December 15, 2007

Caddis, that's neat! It's "only" about 40 miles off for me.

Is it no longer true that certain blocks of IP addresses assigned to certain major national providers can give information for the wrong part of the country? I seem to remember all of AOL's users appearing to be in Virginia or something.
posted by Cricket at 11:16 PM on December 15, 2007

A traceroute to you would also provide some information. It's not uncommon for backbone providers to use place names in the names they assign switching equipment, so getting the last responding hope before yours (as an IP from the traceroute) and then doing a reverse DNS on it could give them an idea of where you are.

For instance, the last hop coming in to me is "GE-1-2-ur03.beaverton.or.bverton.comcast.net". Betcha can't guess where I live, can you?
posted by Steven C. Den Beste at 1:03 AM on December 16, 2007

If you're really serious about avoiding this, you could use an anonymizing proxy such as Tor.
Remember that this is not the same as encryption!
posted by agentofselection at 1:22 AM on December 16, 2007

Intriguingly, I've only ever noticed these things to really work in the United States. In Europe they're wildly out as the infrastructure is too spread out. My IP / hostname appears to be in a town that's 200 miles away from here, just because that's how the UK DSL system tends to work. So.. it's next to useless and those ads are always a dead giveaway when they reference that same town that's nowhere near here.
posted by wackybrit at 6:33 AM on December 16, 2007

Oddly enough, I just moved 100 miles to a different state, and I have a different ISP, but occasionally I'll get ads targeted towards my old location, even though my cache and cookies have been cleared multiple times. I don't believe I've changed my address in Google shopping (or whatever they call it), so I'm wondering if that's the culprit.
posted by desjardins at 9:10 AM on December 16, 2007

Thanks for the info, guys!
posted by phaded at 10:26 AM on December 16, 2007

I love the dating ones, too, especially if you end up on some site like collegehumor or similar where the dating ads are salacious. I live in a very small town that I can honestly say I know most everyone--and none of the half-naked young women live here, you can be sure I would have noticed.
posted by maxwelton at 1:14 PM on December 16, 2007 [2 favorites]