Adware is a software that displays advertisements on the display whether you want them or not. They are not just connected to some websites or free software but are maded to start up whenever your PC is switched on.

Programs like "Eudora" mail client display advertisements in lieu of charging registration fees for use of programs. It helps developers recover program development costs. "Kazaa" the file sharing application comes bundled with at least three ad-ware programs. Two of them serve ads to the desktop while another redirects the user’s internet browser to a search engine with advertiser sponsored web results. Well known ones are: BroadcastPC; Comet Cursor; 123 Messenger, GeoWhere; Network Essentials, Direct Revenue, and so on.

Spyware is a software code that relays information about you and your data without your permission or knowledge. Some just “spy” on you conveying your web habits to marketing companies, while others are “thieves” they access credit card information as well as other sensitive files. In plain terms, it is malicious software that can "get" or take control of a computer’s operation without user knowledge or consent. Termed as “malware” the redefinition of spyware, the programs can:

1. Steal personal information and the address book.
2. Flood the browser with pop-ups.
3. Spam the system.
4. Slow down programs and connection.
5. Hijack the browser and redirect the user to a “con” page.
6. Uses the computer as a server to broadcast porn.
7.  Can cause a crash.

Spyware reaches a PC through innocent URL pages, game demos, MP3 players, search tool bars, and other downloads like "free" software. It installs itself and leaves a mark on the windows registry key. It can hog the computer resources such as memory and hard drive and cause a crash or lock up. Keystroke-logging spyware can steal passwords and private information for thieves.