Adware and Spyware

Adware
Adware is software that presents banner ads or in pop-up windows through a bar that appears on a computer screen. Those advertising spots usually can't be removed and are consequently always visible. These advertisements create revenue for the software developer and are provided with initial consent from the user.

Spyware
Spyware refers to programs that gather and transmit the user's personal details or behavior to a third party, often without the user's knowledge or consent. Spyware is designed to expolit infected computers for commerical gain. Typical tactics furthering this goal include delivery of unsolicited pop-up advertisements.