How do they know where I live?

I occasionally get to a web site that knows I live in Arizona and in Apache Junction. Where are they getting this information and how do I stop it?

- Clyde

This question was answered on November 5, 2005. Much of the information contained herein may have changed since posting.

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There are number of possibilities that would allow certain websites to seemingly know what part of the country you are surfing from.

Everyone that connects to the Internet is assigned an “IP” (Internet Protocol) address, which is a unique number sort of like a phone number.

Your IP address is assigned to you by your Internet Service Provider (ISP) from a pool of addresses that are under their control.

The registry that stores which companies control which addresses and their associated locations is an easily accessible database on the Internet Websites that wish to target ads to their customers will often write a script that checks a visitor’s IP address, quickly looks up the associated location and then generates a location specific ad.

This method of looking up a visitor’s location is rather crude and can be very inaccurate If, for instance, your ISP is headquartered in Seattle and you live in Spokane, the ads that you are served will assume you live in Seattle.

Since Apache Junction, AZ is not known as a nucleus of the Internet, there are a couple of probabilities for what you are experiencing.

If you are connecting to the Internet through a small regional ISP that only has a presence in Apache Junction, then they are registered as such and it would be very easy to determine your location.

If you are connecting via one of the many larger ISPs that have a presence in many markets, the ability to pinpoint your exact location is more likely as a result of an Internet “cookie” and not your IP address.

Cookies are a tool that give websites a sense of memory and allows them to distinguish one user from another Most sites use them to do everything from count the number of unique visitors that they have to delivering customized ads or content

The cookie itself does not contain much information; it acts kind of like a bar code so that websites can lookup the information that you submitted from a previous visit.

Somewhere in the past, you likely filled out an online form that asked you for your address and a cookie was placed on your system that connected you to the information that you submitted

If this site has a reciprocal relationship with other websites or is part of a large advertising network (which many millions are), then all of the participating sites will know your location based on that original submission and the cookie that resides on your system.

If you want to test this theory, you can toss your cookies, clear your Temporary Internet files (both can be done by clicking on the Tools menu, then Internet Options in Internet Explorer) restart your system and then re-visit the site to see if it still knows your location.

If you do clear your cookies, you may also impact the “memory” that desired websites have (such as a weather or financial site) or wipe out a stored username and password for sites that require you to login.

If you are an active online consumer, you may want to manage cookies with a program that will allow you to keep or delete them based on the website

Many low-cost or free programs can be found online at sites such as www.snapfiles.com and www.cookiecentral.com.

About the author

Posted by Ken Colburn of Data Doctors on November 5, 2005

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