We've put Spyware and Adware together because in many ways they are inextricably linked. They are certainly are both intrusive and extremely annoying. Left to accumulate, both types will have a detrimental affect on performance of your PC. Let's deal with Spyware first.

What Is Spyware?

Spyware often appears as cookies or small pieces of program code which are transferred to your computer from internet or from installed software without your knowing. It's purpose is simple enough - to make a note of what you are doing as you browse web and then feed information back to it's originator - all of this while user remains completely unaware of what is going on. Now why would anyone want to know this, you might ask.

Well that answer is simple enough too. Supposing you spend a lot of time looking at gardening sites. You might find that you soon begin to receive a lot of e-mails advertising seed catalogues. The Spyware has sent back information that suggests that you are a keen gardener and more importantly - a potential customer. Likewise, you may find that you start to get a lot of pop-up ads while you are browsing Internet - some related to gardening and some related to kind of other interests gardeners are expected to have.

If you're still not sure what Spyware is all about then take a look at this new video from Microsoft (requires Macromedia Flash Player 7.0.)

What Is adware?

Although just as irritating, adware does, at least sometimes. tend to be a little more up front about itself. Some free software, Kazaa is a good example, fund themselves by displaying pop-up and static advertisements while you are using software. When you install Kazaa software other software is also installed which takes care of advertisement maintenance. In fact, Kazaa will refuse to run if you uninstall advertisement software.

Now it's arguable that funding software this way is perfectly legitimate. After all, commercial television has been funding itself this way for many years. You, as user, have to make a decision as to whether or not you are prepared to put up with advertisements. The problem with a lot of adware is that you don't get that choice. Sometimes software you are installing doesn't tell you that it comes with adware and you only find out after you have installed it when pop-ups begin to appear from nowhere.

Understanding Software Layers of a Computer

By Stephen Bucaro

You're typing in a word processor and you decide it would be nice to have a hard copy. You select File | Print in menu and printer comes to life, feeding out a copy of your document on paper. It seems like a simple process, but in reality your request passed through many layers of software before reaching your printer.

Although you requested print through a menu of your word processing application, that application did not contact printer directly. Instead, aplication made a request to computer's operating system. Remember, today's computers are multi-tasking. That means they can perform more than one task at a time. The operating system mediates priority of multiple tasks requesting to use a hardware device.

The operating system did not contact printer directly. Remember, today's computers can have a multitude of different hardware attached. There are thousands of different kinds of printers, and a computer may have several printers attached. Instead, operating system communicates with a piece of software called a "device driver", specific to printer that you selected.

The device driver did not contact printer directly. Instead, device driver contacted a program called BIOS (Basic Input/Output System). Whereas all programs up to this point had been loaded from computers hard drive, BIOS was loaded from a memory chip. Finally, BIOS communicates directly with electronic circuits of printer.

[Application]--[Operating System]--[Device Driver]-- [BIOS]--[Hardware]

The above explanation describes common software layers of a computer. Each of software layers described above may itself consist of many layers. An application may communicate with operating system through a piece of software called a DLL (Dynamic Link Library).

The operating system especially is constructed of many layers. Sometimes operating system is described to be like an onion. At center of onion is operating systems kernal. Only other layers of operating system are allowed to communicate directly with kernal. The outer layer of operating system consists of programs called services which applications can communicate with directly.