A cookie, also known as a web cookie or a browser cookie, is a small piece of data sent from a website and stored in a user's web browser (in a text file) while a user is browsing a website. Some cookies disappear after user closes his browser while others, known as tracking cookies, remain saved and load the next time user visits the same websites.
These cookies help track user's browsing sessions and load information faster, but create some security and privacy concerns as well. These security and privacy concerns are :
1. Session Data. When you visit a website on a regular basis, such as your email or online bank, you may not have to enter your username and password to get in. That's because the information is being pulled from a tracking cookie. While these cookies encrypt the information they store, if somebody found out the encryption key and acquired your cookies, he could discover your passwords. While the odds of this happening are extremely small, the risk does exist.
2. Tracking Information. When you visit certain websites with advertisements, those ads create cookies that store and track your online patterns. You may have noticed that if you go to a clothing store's website, for example, you'll see ads for that store when you click away to other websites. That's because tracking cookies have relayed this information back to the advertisers, who use it to target their ads. Sometimes, your information may be sold to other companies. Some people view this as an invasion of privacy.
3. Public Computers. While the same general threats exist for traffic cookies saved on public or shared computers as those saved on your personal computer, the much larger amount of people who have access to these computers makes saving traffic cookies more risky. When you finish using a public or shared computer, delete the cookies to ensure that the next people who use the same computer can't access the information.