Understanding Cookies How They Affect Your Privacy


Authored by Dave Mallisk in Internet
Published on 08-29-2009

An internet cookie is a small text file that identifies your computer to the website that created the cookie. When you first visit a website that creates cookies, as do most commercial sites, it sets a cookie on your computer. Cookies let websites conduct marketing research by tracking many visitors. For example, a fashion website might identify changing fashion preferences by tracking which pages within that website have the most visitors.

Cookies are generally benign, and do not affect your privacy. Cookies contain no viruses because cookies can contain only text; never code. Although unscrupulous websites can create malicious cookies (such as adware and spyware cookies), you can help guard your privacy by using an anti-spyware utility and your brower’s cookie tools to manage your cookie privacy.

Internet Cookie Types

Websites can create two internet cookie types, first-party and third-party.

First-Party Cookies – A first-party cookie can be either a session cookie or a persistent cookie:

  • A session cookie exists only while you visit a website. Data in the cookie identifies your computer throughout the session (visit), which helps you perform routine tasks, such as logging into the website and navigating among its pages.
  • A persistent cookie exists until either you delete it or it expires. Each time you visit its website, data from a persistent cookie helps the website track whether it has separately (not in the cookie) stored information, such as:
    • Pages you had preferred during previous visits
    • Personal data you had provided (such as postal address and phone number)
    • A list of items you plan to buy (a ’shopping cart’)

Third-Party Cookies – A third-party cookie is a persistent cookie sent by a website that has placed one or more ads (typically banners and/or pop-ups) on a website you visit. As a simplified illustration, here is a third-party cookie tracking your visits to imaginary websites:

  1. AdSite.com places one or more ads on each of three websites, FirstSite.com, SecondSite.com, and FourthSite.com. On each website, AdSite.com also sets an identical copy of its third-party cookie.
  2. When you visit FirstSite.com, it requests ad contents from the server at AdSite.com. As part of this request to display ad contents, it also forwards data from your AdSite.com third-party cookie to AdSite.com, which records your visit. If you do not yet have this cookie, AdSite.com sets it on your computer, stores it on your hard drive, and records your visit.
  3. When you visit SecondSite.com, it requests ad contents from AdSite.com, and sends tracking data to it from your AdSite.com third-party cookie.
  4. When you visit ThirdSite.com, it neither requests ad contents from AdSite.com nor sends tracking data to it from your third-party cookie because ThirdSite.com contains no AdSite.com ads.
  5. When you visit FourthSite.com, it requests ad contents from AdSite.com, and sends tracking data to it from your AdSite.com third-party cookie.

So far, AdSite.com has tracked your visits to FirstSite.com, SecondSite.com, and FourthSite.com. Until you delete AdSite.com’s third-party cookie (or until it expires), it tracks each visit you make to any website that displays one or more AdSite.com ads.

Managing Your Cookie Privacy

As part of an overall security strategy for your computer, you should manage your cookie privacy. In addition to simply surfing wisely and avoiding hazardous websites, you can manage your cookie privacy through an anti-spyware utility and your browser’s cookie tools.

Anti-Spyware Utilities – You can run an anti-spyware utility to find and remove malicious cookies (and other spyware). If you do not already have an anti-spyware utility, you can obtain it as part of a security suite. To compare various security suites, see: PC Magazine Windows Security Suites.

Your Browser’s Cookie Tools – According to instructions for your browser (such as Internet Explorer, Firefox, or Google Chrome), you can use its tools to:

  • Delete all cookies currently on your hard drive. This deletes all your computer’s existing malicious cookies.
  • Block all cookies so that no website can set any cookie on your computer. This is inconvenient because it prevents easily surfing most websites.
  • Block all third-party cookies. This blocks some, but not all malicious cookies. Therefore, you should also run an anti-spyware utility as explained above.

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