information system security, computer science homework help

Discussion Question:  Chapter 11 of thetext discusses malicious software such as viruses, spyware and malware.Most people using desktop computers in the past two decades have comeacross these items at some point or another.What are viruses?What is spyware?What tools and practices can be employed to help prevent such items from getting on your computer?i just need 250-500words for the above question with atleast two references with links.thank you.