Tech Q&A: What are cookies, and are they dangerous?

By Anick Jesdanun, The Associated Press

Q. I've been hearing a lot lately about "cookies" on my computer. What are they, and are they really dangerous?

A. Cookies have been getting a bad reputation lately because some are linked to spyware and adware, programs that often sneak onto your computers. Many anti-spyware programs identify cookies as threats because Web sites can use them to target ads based on your surfing habits.

But cookies are much more than that.

Fundamentally, cookies are small data files your Web browser uses to help sites remember who you are. They were invented at Netscape Communications Corp. a decade ago and incorporated into the then-reigning Netscape Navigator browsers to make Web surfing more efficient. Other browsers soon adopted cookies, too.

Without cookies, each interaction with a Web site would be treated as a new visit. The site would have no way of knowing that the page you just called up and the one you called up five minutes ago were summoned by the same person.

That's often not a problem for basic Web pages.

But for commercial Web sites, it can be.