You visit a website that requires registration, and you create your own unique user-name and password combination. Then when you comeback to that site some day later, the site magically seems to know who your are, and greets you by name! Apparently it knew your login and password, and logged you in automatically!
Have you had this kind of experience? It sure feels kind of spooky. Of the millions and millions of users who use that website (in the case of very popular websites) every day, how can the site identify each and every user? You thought the internet was free and anonymous, is someone keeping a tab on you?
Hey, relax. This isn't a spy game. You aren't the innocent victim of some bloody international conspiracy of espionage and skulduggery. It's just cookies.
No I'm not joking. It's really cookies. Not the edible kind of course I'm talking about internet cookies. Yes, the internet has cookies too. And you thought you had seen everything!
Internet cookies aren't made of flour and sugar, but of bits and bytes. They are really very small files which are just called cookies. Perhaps they gave this name to it because they are small, and normally die after some time, exactly like cookies tend to crumble when left out for too long.
When you visit a website, that website sometimes wants to be able to remember you when you come back to it later. For this purpose, it asks your browser to accept a tiny file that contains information about when and from what internet location you accessed that site, and what actions you took. If your browser accepts this file, it is saved at a special location on your hard disk.
Then when some time later you go back to that site again, that site asks your browser to see whether there is any cookie from that site on your hard disk. If the browser answers in the affirmative and shows the cookie to the site, your identity is established. Now the site knows who you are, when you came to that site last, and what you did there. It may even know you by name, login name and password, if you provided that information to the site earlier. Thus it can magically or frighteningly seem to know all about you!
As you can see, cookies are harmless little helpful objects that you don't really need to worry about. Or are they?
Cookies can be less than innocent when used illegally by shady websites for unlawful acquisition of information. Cookies can be used in a way that they know all about which sites you visit, and on which links you prefer to click. This information can then be used to illegally build a profile for your internet usage, and then this profile can be sold to advertising firms. These firms then send you targeted ads in the form of pop-ups, unsolicited e-mail or other forms of annoying unwanted material.
How can you fight against illegal cookies? How do you know which are illegal? What can you do about them?
First, you need a good browser that gives you options that are fine-tuned enough for this kind of filtering. You can find two such good browsers here and here. Both of them are free downloads. Then in the browser of your choice, set the options in a way that no cookie is allowed from third-party websites. It's a bit difficult to explain here why you need to do this, but trust me this is the way most illegal cookies are set.
Also, review the list of accepted cookies from time to time there is an option in both of the above browsers to view these. Delete anything that is from a website that you don't recognize. If this breaks some of your surfing experience, you can always go to the relevant site and have them set again.