Home Forums Networks & Cross-Platform Networking What are the ways a site know who I am?

If a website seems to know who you are without ever making an account or divulging info,
Beyond IP address, how else do they know who you are?
Cookies? what else? thanks.

In theory, cookies saved from a different website, (and java variables and other cache info) should not be accessible from other pages and scripts. From time to time there are security holes that are exceptions. I believe the scripts that set the cookies can specify what domains can access them, maybe it's ignorance on their part when things leak that way?

Other than that, most web browsers have a "form autofill" feature that remembers what values you tend to put in fields like "name", "address", "phone number" etc. Forms can tag fields with those descriptions, and in most cases, when you type in information into a named field that matches what you've put into the same named field on another page, it will offer to auto fill the rest of the fields on the form that it can.

Form Autofill does not get info from the web site, it comes from your computer. And it's not sent to them unless you choose to allow the autofill to occur and then submit the form, so it's entirely up to you. You can let it autofill all the fields, and then change some of them. I do this since I use multiple email addresses for different places I order from, and I have to change the email address after it fills in all my other info.

You can clear the autofill or disable it completely in most web browsers if you want to.

Other than that, some pages may say "Welcome back, Jason!" at the top for example when you go to them. That's coming from a cookie the web page set last time you logged in at that web site, and has probably kept you logged in. It may still have your name but not your password and require you to login. That information is not shared with other web sites by default. Most cookies for login expire after a few days, a week, a month etc. A few never expire.

Some people consider cookies a violation of privacy, and some set their computer to clear cookies when they quit their browser. I personally think they're being paranoid. As a comparison, they're a lot less invasive than say, those loyalty supermarket cards everyone has on their keychains. Those things track your shopping in great detail and tie that information to you personally, not anonymously. Cookies are more for your convenience than anything else.

Virtual,
they know who I am before filling in ANYTHING.
And I've cleared cookies and IP, so I'm stumped.
and ideas?
Also, cookies just help you get to a site faster, connection wise. They don't auto-log you into a site, correct?

V1 already mentioned Autofill. Have you turned everything off in Safari > Preferences > Autofill? In Safari > Preferences > Security have you disabled (UNchecked) Location Services?

Cookies can and do a LOT more than simply log you on faster, it all depends on what the site developers put into their cookies when you access their site. For example if you set Safari > Preferences > Security to Accept cookies: Never you will disable the ability to create cookies, but it is unlikely you will be able to use any web store shopping basket or financial services web site. In fact that will also disable several "features" of this web site.

Joe, thanks.
I just switched last week to Firefox after years of instibility and frustration with Safari.

Autofill, not issue in this case: the site (craiglist), recognizes me the minute I want to post an ad. this is without filling in anything whatsoever.
In past, changing the ip would do the trick. but not now. Even deleting cookies is not working.

Back to subject of cookies. Don't cookies just connect you to a site faster, ie connection speed thing, or are they also part of the function that logs your user/pass as well?

Cookies have nothing to do with speed.

Cookies are a way that a Web site can store information on your computer, so that when you visit the Web site again it can retrieve that information. Some cookies are used to store things like your username and password. Some cookies store things like the number of times you visit. Some cookies store information about your browser. Some cookies store things like user interface settings you specify on the site. They can store whatever the Webmaster wants them to, really.

There are many ways a Web site can remember who you are. Some of the most common are cookies and IP address, but there are others as well. Autofill information you have set in your browser, for instance.

Some Web sites can store a "fingerprint" of your computer. Your browser sends all sorts of information when it connects to a Web site, such as the browser kind, the browser version, the resolution of your computer screen, the size of your browser window, and so forth.

The Web server can request other information if it wants to, including a list of browser plugins you have installed, what version they are, a list of the fonts you have installed, and other information. Since it is very rare that two computers have the same exact browser version, plugins, and fonts installed, this information can create a unique "fingerprint" that identifies you. There is an article about this here and a Web site that will test your browser for its fingerprint here.

Most Web browsers will also tell Web sites what your browsing history is, and Web sites can see other sites you visit. Safari 4 does not do this, but older versions of Safari do. Firefox lets Web sites see a history of other sites you have visited. So do Chrome and Opera. You can test your browser to see if it shows your history here.

Great post Tacit!
So cookies are the main tool that allow me to return to sites without having to re-enter user/pass?
That's a drag because I think it's good to clear all cookies sometimes.

I'm on Firefox now, anyway to not have that history be revealed to badly-- I checked out that link - it's very bad what's going out.

I assume it does not do this with private browsing.

What about the fingerprint. What can one do to scramble that?

And you are saying a website can see my name and other autofill stuff address, without me entering autofill? Just by it being there?
I'm using a firefox plug in for that. any recommendations or protection on that topic? So I understand you right? People can see what I've entered in autofill even though I have not filled anything?

Other ideas? To be honest, I tried first to connect to this ad site of which I had never used Firefox before (I was on Safari back before), and it had me nailed even after a cookie purge and an ip change.
Someone on another forum says they may block or identity a group of ips from a isp, that seems far-fetched to me.

Yep, cookies are the most common way for a site to remember who you are when you visit. Your username is stored in the cookie, so the site recognizes you when you return.

Firefox always exposes your history. There's no way I know of for you to block it; the Firefox programmers will have to do that.

Scrambling a browser fingerprint is more difficult. Your fingerprint will change when you change plugins, change browser versions, change your screen resolution, or change your fonts, but since this information can be made available to a Web site, it can still be used to fingerprint you.

How a site might identify you after you dump cookies and change IP addresses, I can't answer. It depends on what the site's doing. It's not likely it's looking at a browser fingerprint (and in any event changing browsers will change that). A site can block an IP range, but that's rare.

This topic shifted gears to a non-troubleshooting discussion on IP blocking which has been moved into the Lounge where it can continue.