How does location-based web advertising work?

January 7, 2006 12:39 AM

How does location-based web advertising work?

Over the last year, I have noticed that some websites have been carrying location-relevant ads that aren't necessarily related to where the website is based, but instead, where the user is surfing from. For example I have seen Canadian (Bell Telephone) ads in American websites. I have also seen Google text-ads that carry titles like - "Find Potted Plants* in Toronto!" when I only searched for information on Potted Plants.

I have, based on my limited knowledge, excluded some explanations for this. My Google/Gmail account does not specify what city I live in. My computer is set to Eastern Standard Time and Canadian English, but I am sure that I never specified what city or even province I am in. I have scanned my computer for spywares, I run standard IP blocking programs and have a fairly good firewall. So that rules out most user end vunlerabilities.

So how do advertisers know where you are surfing from? I have noticed location based advertising popping up even during times when I am surfing on public terminals. I am guessing that since google directs me to google.ca whenever I type in google.com, some type of IP filtering is at work. This however, is scary.

So, are there any articles/studies/even companies that can confirm or reject this semi-festering paranoia?

*The freakiest ad has been - "Meet someone special in Toronto" with profiles (which I'm sure are faked) of people living in the city.

posted by phyrewerx to Technology (10 answers total)

Best answer: It's based on your IP address. Here's an example of a service that determines the geographic location of an IP address. Something like this would be used by the machine serving ads to customize them geographically.
posted by bachelor#3 at 12:49 AM on January 7, 2006

I'd guess that some sites go beyond IP address and try to correlate in other information since that info can be pretty inaccurate for a lot of users (like people who use big ISPs like AOL)

I hadn't thought about probing for timezone using javascript (I think that's possible). Also, are you sure that you've never told Google anything about where you live (for example, now you need to use a mobile phone number to get an invitation code).

Ad networks might notice that you tend to visit member sites that tend to attract local residents and infer from that that you live in the area as well.
posted by Good Brain at 1:20 AM on January 7, 2006

Nothing strictly related to Google at all - and it is based on IP address. It is inaccurate, but accurate enough for the purposes of advertisers. There are databases associating blocks of IP addresses with locations, and this makes sense even for large ISPs like AOL, because they tend to have a set of IP addresses for each city's POP.
posted by Jimbob at 1:39 AM on January 7, 2006

I run standard IP blocking programs

There is no such thing. If two computers on the internet establish a TCP connection (which involves a three-way handshake) then both ends know the IP address of the other system with absolute certainty. There is no way that you can "block" an IP address and still establish such a connection.

Most of these "hide your IP address!" crapware really just amount to using a proxy. If you proxy your traffic through a third party then the remote end will see the IP address of the proxy and not your address, so in theory this is a method of obfuscation -- but there is still no "blocking" going on whatsoever. The thing is, some proxies do reveal the end-destination IP address (through such things as the "X-Forwarded-For:" or "Via:" HTTP headers) so this is not always an effective method. And in your case it looks like whatever you are using is not doing a thing, unless you just happen to be using a proxy in the same general geographical area.
posted by Rhomboid at 2:23 AM on January 7, 2006

Rhumbold is exactly right. It is based on IP address identification. This is by no means perfect but works most of the time. Why is it that scary? You give out your IP address when you're out on the internets, that should be common knowledge. You can use a third party proxy although that's kind of tricky at times. The best solution if you're completely paranoid is probably using an ISP with a dynamic IP address provided that gives a frequent enough update time. But hey, it's not like the NSA don't know everything about your secret terrorist website activities already. And who else really cares unless you're after child porn or whatever dodgy like that?
posted by keijo at 4:47 AM on January 7, 2006

Response by poster: Thanks everyone. From further research I found this - http://www.isapilabs.com/products/countrylocator/faq.htm . I guess they really are just filtering based on ip addresses.

Keijo - Perhaps it's not scary, you're right, I might have used the wrong term. Surfing any website will expose to the webservers what ever browsers you are running and other information, that I accept. However, I found the initial idea of location-baesd advertising disconcerting because of the possibility that advertisers online have more information about who I am than I'm willing to give. My question was more about - am I giving advertisers more information while surfing more than my software configuration and my os? I know that car dealerships that send ads to my home got my name from some database, likely my credit card, but I have never made the connection that I have signed up for something online in which I gave them my geographic location and allowed them to send out that information to be used in ads for other sites. I find the argument - "You have nothing to worry about if you haven't done anything wrong" unacceptable and simplistic. Governments, esp law enforcement, if they want to, may have internet tracking abilities beyond geographical identification. That I accept. But from a privacy standpoint, I dislike the possibility that advertisers from Long Distance Telephone companies to "Meet Singles Online" sites have found some insidious way of tracking where I live beyond cookies and server logs (like Good Brain's javascript idea).

Rhombold - I mean a program that blocks certain spyware/adware sites based on an IP table. Things like Peer Guardian.

Good Brain - Yes, I am sure I have not provided google anything about where I live. GMail invitations before didn't need a mobile number.
posted by phyrewerx at 7:58 AM on January 7, 2006

Best answer: They can only see the location of the owner of the IP addresses (this is your ISP, not your computer). Like "Good Brain" says, this is often inaccurate for large ISPs such as AOL.

Here's an example of a company selling this location tracking service to website.
posted by null terminated at 8:45 AM on January 7, 2006

*websites.
posted by null terminated at 8:52 AM on January 7, 2006

If it bothers you, try tor.
posted by Rhomboid at 9:01 AM on January 7, 2006

While AOL does dole out IP addresses associated with local POPs for its users, all Web access done through their client goes through one of their proxies. Many other ISPs also use proxies, often transparently. So determining geographical area by IP address is less accurate than it could be. But as others have pointed out, probably accurate enough. You can just filter out known proxies and show them generic or nationwide ads.
posted by kindall at 9:13 AM on January 7, 2006