How to combine the sentences
7. Some people use the terms viruses, worms, and Trojan horses interchangeably.
Each has unique characteristics.
8. A virus is a type of malicious code.
A virus requires the user to actually do something before it infects a computer.
9. One action that could activate a virus is opening an e-mail attachment.
Going to a particular Web page is another action that could trigger the downloading of a virus.
10. A worm is similar to a virus and is considered a subclass of a virus.
Unlike a virus, worms have the capability to spread without any human action.
11. The victim computer becomes infected.