Could someone please enlighten me, either on a technical level or high level if that detail is not feasible, on how tracker cookies and beacons work.

Particularly, how information on my browsing habits (shopping suggestions) can be persisted between different machines even when I only use one for work, never logging into personal accounts.

I'm not too concerned with my ISP knowing what I've visited but I resent companies collecting data for targeted advertising.

I already use the Ghostery add-on for Chrome. Do I need to start using VPN services? I didn't think companies were able to get information on your internet usage this way anyway.

Many thanks everyone.

  • 1
    Actually, I rather suspect Chrome collects data for Google Analytics (which is responsible for a large percentage of the internet's ads). So switching to Firefox might be a good way to start
    – KnightOfNi
    Jul 16, 2014 at 21:56
  • What research have you done? There is a lot written on this subject, and I'm not sure there's much value in asking people to re-type up stuff that's already well-documented elsewhere. Do a bit more research; you should find lots of information about it. You might also want to refer to the site faq and help center. As the help center explains, "IT Security Stack Exchange is for Information Security professionals..." (I've bolded the key term).
    – D.W.
    Jul 23, 2014 at 23:37
  • Thanks for the feedback. I appreciate your point however this question is supplementing research I have already done and as I'm expanding on the basics to ask a more in depth question. Everyone has to start somewhere. I think that in any subject there are no stupid questions. If as you say this is intended for only professionals and I have violated that then the site should ask payment for membership and proof of qualifications. It does not and as far as I can see it's a free and open forum for learning. Also, one user was kind enough to reply and that might help someone else too.
    – user49984
    Jul 28, 2014 at 9:05

1 Answer 1


A Cookie allows a website to place a small file on your computer, which is usually used as an "identifier" that then can then go do a query against in their database and go "ah, this is customer X who was browsing Y earlier today" - normally (outside of security exceptions which are patched), a site can only read it's own cookies, however, many rely on a 3rd-party cookie, such as google (adwords), to handle some of the work, allowing them to focus on their own things, instead of creating their own website completely, so they may have a small piece of code that says "go to google and insert a small portion of the website into this corner as an ad" - that code does so, and leaves behind a cookie, so that then google can check for the presence of this cookie on the page that the ad led to (and thus count if you clicked on it or not) - now many websites could use the google ad service (or any other large ad service), and google can "recycle" the cookies, and use them to track you from site to site

up till now everything has occurred on a single PC - now you go to another computer, and the same process goes on, and thus google has two cookies with information about sites visited from two computers - if the browsing habits are similar enough (such as you look at profile XYZ) on both computers, google can associate that "people who look at profile xyz are likely to shop for qwerty" - and begin to show you ads for qwerty, even if you never logged in - probably the best example of this is music services that "suggest" music based on what others who listen to similar music like, even if you have never heard of the band before, and with a relatively good accuracy - not perfect, but then there isn't too much harm in them guessing wrong either (usually - exceptions will always exist), and their profits are better when they do guess, so they try their best to do so.

edit: I am not sure about Ghostery, however most browsing would be severely restricted if cookies were completely disabled, and your still using Chrome - I imagine Google wouldn't allow it in their store if it did it's job too well..


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