You probably know that Windows and your favorite web browser, whether that’s IE, Firefox, Opera or another, have a number of features designed to make YOUR life easier when you are using Windows or surfing the web.
One of the ways they do that is to create one or more caches, that is, temporary copies of downloaded images and other work files.
Many programs clean up (delete) their temporary files when you exit the program. Web browsers do not, although most can be set to do that. It takes longer to exit the program, though, so that option is turned off by default.
Similarly, IE, Firefox, Opera and other browsers will offer to remember your passwords when you visit web sites, if the site requires you to log in. Whether you choose to let it save the password or not is your own choice. Fortunately, you can make the decision on a site-by-site basis — it’s not an all-or-nothing decision.
Cookies provide a lot of useful functions on the Internet. But, first, what is a cookie?
When you connect to a web site normally, that is, with a standard http connection, you’re only connecting for that one message. When you go to the next page, that’s actually an entirely new connection. As far as the Internet communications protocols are concerned, each request is independent.
Web developers and web browser developers have created sophisticated methods to make it seem like you’ve got a continuing connection — that’s one way a cookie is used.
This is the cookie function that is blown all out of proportion by the anti-spyware companies. Cookies are easy to find, so it’s easy for the program to say "I found Spyware!" That’s why you’ll find vastly different numbers of “spyware items” found on your computer depending on which antispyware you use — some seem to declare ANY cookie to be spyware.
What do I do with cookies?
I don’t worry about them. I have my web browsers set to accept them automatically.
I’m more worried about the amount of space that Windows assigns for Temporary Internet Files. Read more in Setting a Reasonable Temporary Internet Files Limit
So, what’s the big issue with spyware and adware, if it’s not cookies?
The problem is that there are slimeballs in the Internet world who want to actually install their programs on your computer so that they can monitor what you do and capture your user ID’s and passwords.
They also want to put pop-up ads on your computer, install other advertising and spyware (they can get paid for installing other people’s nasties, too), redirect your search queries to their search sites, redirect your banking or business to their fake web sites.
Also, these programs don’t play nicely with your computer. Usually, the first thing installed is a "downloader" which handles installing a lot more junk. In addition to spying on you, feeding you their ads (and even overwriting website ads with their own ads!), these programs slow down your computer and can even make it difficult to boot.