You can get spyware on your computer when you visit certain websites. A pop-up message may prompt you to download a software utility that it says you need, or software may be downloaded automatically without your knowledge.
When spyware runs on the computer, it may track your activity (e.g., visits to websites) and report it to unauthorized third parties, such as advertisers. Spyware consumes memory and processing capacity, which may slow or crash the computer.
Good antivirus and endpoint security solutions can detect and remove spyware programs, which are treated as a type of Trojan.