A computer cookie, also referred to as an "HTTP cookie," is a small text file that contains a unique ID tag, placed on the user's computer by a website. In this file, various information can be stored, from pages visited on the site, to information voluntarily given to the site. These tiny files provide practical benefits to both users and website operators, and generally make surfing the net a smoother experience than it otherwise would be. Nevertheless, privacy advocates tend to be wary of them, since many users are unaware of exactly what information is collected, and how the information may be used or shared.
Types of Cookies
There are two types of computer cookies: temporary and permanent. Temporary cookies, also called session cookies, are stored for a short time and then removed as soon as the browser is closed. Permanent cookies, also called persistent cookies, are stored for a long time on the user's hard drive and, if deleted, will be replaced the next time the respective site is visited.
The temporary cookie is very simple. It works by setting aside a little bit of browser cache memory to retain information about a user's activities during his visit. After putting a selected purchase in a shopping cart, for example, the user might continue to search the site for additional products without having to go through a separate checkout for each item. Once the browser is closed, however, all temporary cookies are lost. Return surfers are not recognized, shopping carts are empty, and any other forms or information will have to be provided again.
By contrast, permanent cookies make it possible for a site to recognize a surfer on a continuous basis. This is accomplished by transferring a text file with a unique ID tag to the visitor's hard disk, while maintaining a matching file on the server. On subsequent visits, the browser automatically hands this cookie over, allowing the site to instantly pull up the matching file. Persistent cookies can exist for years, unless deleted, or until the cookie's internally defined lifetime has passed. Today, permanent cookies are the most common type of cookie used.
How Cookies Are Used
At their most basic level, a website uses computer cookies to log when an individual visits, which pages are viewed, and how long the visitor stays. If he or she returns at a later date, the visitor’s cookie triggers the log of previous visits, and amends it to include what happened during the new visit. If personal information is offered on any of these visits, it is instantly associated with the "anonymous" ID tag, and consequently, the entire profile. In this way, a site can more easily monitor changing trends and other statistics among its visitors. Over time, permanent cookies have also resulted in some initially unanticipated uses, such as web profiling.
Marketers have developed a substantially broader application for cookie profiling. Having advertising rights on many of the most popular websites, marketers can now pass third-party cookies to surfers. This allows them to recognize individuals as they travel between different sites, logging comprehensive profiles of people's surfing habits over a period of months, or even years. Sophisticated profiling programs quickly sort the information provided by computer cookies, categorizing targets in several different areas based on statistical data. Age, income level, and even sexual orientation can often be determined with varying degrees of accuracy through cookie profiling, along with many other characteristics. Much depends on how much a person surfs, and where he or she chooses to go online.
As a result of public outcry in response to hidden profiling, cookie controls are now included in web browsers to allow users to turn cookies off — options that were not available in 1995 when permanent cookie technology was first introduced. Cookie controls also allow user-created lists for exceptions, so that a user can turn most cookies off, for example, but allow them from sites where computer cookies are put to a desired purpose. Third-party cookies often have their own controls, as they are normally placed by marketers.
As a concept, the computer cookie dates back to 1994. In that year, it was adapted as a tool for the World Wide Web by Leo Montulli from a similar technique, called "magic cookie," which was used in UNIX® systems. This is also the origin of the term itself. It was not for another couple of years, however, that the cookies became widely known to the general public. In 1996, articles about them began appearing in the mainstream press, many of which raised concerns about privacy, and in turn inspired the changes in web browsers that ultimately gave users more control over how cookies were implemented on their individual machines.
Are Cookies Dangerous?