What is cookie? (From wikipedia)
What is Cookie?
Adapted From Wikipedia: LEARN MORE
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An HTTP cookie (also called web cookie, Internet cookie, browser cookie, or simply cookie) is a small piece of data sent from a website and stored on the user's computer by the user's web browser while the user is browsing. Cookies were designed to be a reliable mechanism for websites to remember stateful information (such as items added in the shopping cart in an online store) or to record the user's browsing activity (including clicking particular buttons, logging in, or recording which pages were visited in the past). They can also be used to remember pieces of information that the user previously entered into form fields, such as names, addresses, passwords, and credit-card numbers.
Cookies perform essential functions in the modern web. Perhaps most importantly, authentication cookies are the most common method used by web servers to know whether the user is logged in or not, and which account they are logged in with. Without such a mechanism, the site would not know whether to send a page containing sensitive information, or require the user to authenticate themselves by logging in. The security of an authentication cookie generally depends on the security of the issuing website and the user's web browser, and on whether the cookie data is encrypted. Security vulnerabilities may allow a cookie's data to be read by a hacker, used to gain access to user data, or used to gain access (with the user's credentials) to the website to which the cookie belongs (see cross-site scripting and cross-site request forgery for examples).
[1] Tracking cookies, and especially third-party tracking cookies, are commonly used as ways to compile long-term records of individuals' browsing histories — a potential privacy concern that prompted European[2] and U.S. lawmakers to take action in 2011.[3][4] European law requires that all websites targeting European Union member states gain "informed consent" from users before storing non-essential cookies on their device. Google Project Zero researcher Jann Horn describes ways cookies can be read by intermediaries, like Wi-Fi hotspot providers. He recommends to use the browser in incognito mode in such circumstances.[5]
Third-party cookie
Normally, a cookie's domain attribute will match the domain that is shown in the web browser's address bar. This is called a first-party cookie. A third-party cookie, however, belongs to a domain different from the one shown in the address bar. This sort of cookie typically appears when web pages feature content from external websites, such as banner advertisements. This opens up the potential for tracking the user's browsing history and is often used by advertisers in an effort to serve relevant advertisements to each user.
As an example, suppose a user visits
www.example.org. This website contains an advertisement from ad.foxytracking.com, which, when downloaded, sets a cookie belonging to the advertisement's domain (ad.foxytracking.com). Then, the user visits another website, www.foo.com, which also contains an advertisement from ad.foxytracking.com and sets a cookie belonging to that domain (ad.foxytracking.com). Eventually, both of these cookies will be sent to the advertiser when loading their advertisements or visiting their website. The advertiser can then use these cookies to build up a browsing history of the user across all the websites that have ads from this advertiser.
As of 2014, some websites were setting cookies readable for over 100 third-party domains.[26] On average, a single website was setting 10 cookies, with a maximum number of cookies (first- and third-party) reaching over 800.[27]
Most modern web browsers contain privacy settings that can block third-party cookies. Google Chrome introduced new features to block third-party cookies. Henceforth, they are now blocked by default in Incognito mode, while a user can choose to block them in the normal browsing mode too. The update also added an option to block first-party cookie too. [28]
