11.1 What are they?
When you visit a website the chances are that it will deposit a cookie on your computer. A cookie is a plain text file that cannot pose any threat to your computer and cannot pass on viruses. Therefore, cookies are harmless. Or are they?
The cookie protocol was developed to enhance the experience of using the Web. The cookie that a website deposits on your computer contains information about that website. When you revisit the site it recognises you, or more accurately your computer, and customises its service to you. For example, these websites might greet me with 'Welcome Dave Phillips' when I revisit them.
The way in which some websites implement cookies has caused privacy problems. The Internet Engineering Task Force (IETF), formed in 1996, set out to change the way that browsers handled cookies. Initially users were not aware that cookies were being added to their computers, but the IETF advocated that the standard implementation of web browsers should at least warn the user, by default, before accepting a cookie.