Spyware is more dangerous than a virus. It can steal personal data and track your internet habits. It might be concealed in a free screensaver or other software that you download. Computer safety expert Leif Wheeler advises us to be aware of any offer of free software. Many times, spyware is hidden in legitimate software. Be cautious of deals offered by well-known companies. Crooks and thieves often create web sites that resemble Adobe, Google or Microsoft, says Wheeler. They instruct you to download upgrades which secretly contain spyware. Common sense should tell you to download things like screensavers or wallpaper only from a company's registered web site. Have a safety talk with anyone who uses your computer. Run an anti-spyware application. The schemes for stealing are the same, notes Wheeler. What's changed is the technology. The rest of us have to try to stay one step ahead.

There is a type of spyware that the New York Times has labeled as Stealware and what spyware researcher Ben Edelman refers to as Click Fraud, also known as Affiliate Fraud. The most notable vendors of this kind of spyware are 180 Solutions and WhenU. This spyware redirects the payment of the rightful affiliates commission to the account of the spyware vendor.

An instance of spyware rarely "exists" alone. An afflicted computer can rapidly become corrupted with a lot of spyware devices. Frequently, users will notice erratic behavior and a decline of the systems operation. Spyware contamination can cause considerable inappropriate CPU activity, network traffic, disk usage and the slowing-down of the legitimate uses of these resources. Stability issues, system crashes and application crashes are also very common. Spyware which disrupts the networking software normally causes problems connecting to the Internet.

A Trojan horse, by definition, sneaks in a danger-some program cloaked as something acceptable. Many spywares get spread in this way. The representative of the spyware presents the program as a suitable utility, for example, as useful software or as a web-accelerator. Users then install the software not suspecting that it could do harm to their computer. A classic case of this is Bonze Buddy, a spyware application designed to trick children, claims that: He will explore the Internet with you as your very own friend and sidekick! He can talk, walk, joke, browse, search, e-mail, and download like no other friend you've ever had! He even has the ability to compare prices on the products you love and help you save money! Best of all, he's FREE!

Often times, spyware programs are revealed by visibly presenting advertisements. Some spyware simply displays pop-up ads on a pre-determined schedule. For example, a pop-up may appear when the user opens a new browser window. Yet other types display ads when the user visits a specific type of site. Spyware developers use this as a selling point when pitching their wares to advertisers who want to buy ad placement in pop-ups shown when the user lands on a particular site. It is also one of the reasons why spyware programs collect and store information on user behavior.