What can a website I visit tell about me?

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Summary: Websites can collect a fair amount of information about you. In this first step we look at what every website sees no mater what it does.

This turns into a fairly complex answer pretty quickly. It's both more, and a lot less, than you might think.

This article will start by covering what every website sees.

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I'll use a simple web site, like this one as an example. Here's an actual log entry that shows what's provided when someone visits the URL http://ask-leo.com/who_is_leo.html:

There are several interesting bits of information there:

• 64.105.215.206: the IP address of a visitor.

• [22/Sep/2008:15:36:26 -0500]: the date, time and time zone offset that the visitor came by.

• GET /who_is_leo.html HTTP/1.1: the operation (GET), the page requested, and the protocol version to be used.

• 200: the return code. In this case 200 means success.

• 12120: the size of the response - in this case the size of the file "who_is_leo.html" without any of the embedded images which are retrieved with separate requests.

• "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.1) Gecko/2008070208 Firefox/3.0.1": this fairly long and obscure string known as the "User Agent" string identifies the browser used (FireFox 3), my operating system (Windows XP), and occasionally some other things that the browser chooses to put in there.

As you can see it's both a lot, and not really so much.

Your IP address doesn't really say much. I've written about this repeatedly, but unless you're the police with a court order, the best a web site owner can tell is your ISP, and roughly where on the planet you are - sometimes as accurate as your neighborhood, and sometimes only as close as your continent.

What a website cannot do is use this information alone to identify you by name, phone or address.

And it certainly cannot tell things like your computer name, profile, history or email addresses.

However.

There are two interesting exceptions to that.

Sites can typically remember what you've told them. So, for example, if you tell a site your username is "Fred", say by logging in, then that site can, indeed, remember that if it chooses to do so. This is typically by using cookies.

Tracking. Tracking's a loaded term, but the fact is that there's a lot of it going on, often in places and ways you don't necessarily consider: more cookies, toolbars and now even ISPs are getting into the act.

So far we've seen the bare minimum that every website gets whether or not they ask for it.

I start to look more deeply into cookies and tracking in What are browser cookies and how are they used?

Related:

• What are browser cookies and how are they used? Browser cookies are a way that web sites can leave information on your computer that they can use when you return to their site. Simple and powerful.

• When I visit a web site, can the server identify me? A server can easily identify any users that visit their web sites. However, there are services that will allow you to surf anonymously.

• What can people tell from my IP address? People can tell very little from your IP address. They cannot, for example, tell who or where you are. How much they can tell varies a great deal.

Article 12707 | Posted September 22, 2008