Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am a bit confused with the possible security risks with tracking cookies.

From what I have read, if i am on a website and they have ads from a service like doubleclick, doubleclick will place a cookie on my computer. It assigns me a unique id and then makes a note that i was on website When I visit another site that uses doubbleclick, lets say, a script runs and sees that i have a cookie from doubbleclick and then doubbleclick checks what website I was on in the past. It then displays relevant ads and content on

My questions are:

1st, How does it work?

2nd, if I accidentally click on a malicious website that has doubbleclick ads, can that website get a copy of all of the data that doubbleclick has on me, and sell all of my browsing history to a marketing company?

Or does doubbleclick keep the web history it has on me to itself and just give the website relevant ads to display?

Also, I have read rumors that programs like smileycenteral track web usage through cookies. I don't understand how this would work, as why would someone need to download a program to let a company use cookies to track you? Couldn't they just track you using tracking cookies when you visit their website?

share|improve this question
Not certain if I understand why this was closed. There are 650 questions concerning cookies here. – Snesticle Nov 1 '12 at 20:19
1) yes (more or less) 2) you should check doubleclick's privacy policy 3) Programs running on your machine have MUCH more access than ad sites using cookies. In theory they could track EVERYTHING you do with your computer. They certainly have access to your entire browsing history (not just participating customer sites) and may have the ability to change what ads are presented to you without the current site's participation. – Chris Nava Nov 1 '12 at 20:26
  1. the tracking cookie is most likely just an identifier (like a session-hash) linking your visit-history to a database-record on doubleclick's side.

  2. you are correct with the second statement, ad companies just provide you with the code for a "frame" in which they display whatever content they see fit, eg. by analyzing your content-keywords, the visitors history, etc.

  3. i dont know about that rumor but having an installed program could possibly make cookie-tracking more persistent so they could trace you across browsers or after clearing all temp. web data

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.