Which of the following is a type of malware that is secretly installed on the user’s personal computer and collects users’ information without their knowledge?

A.
Worm

B.
Virus

C.
Spyware

D.
Adware

Explanation:
Spyware is software that gathers information about a user without his knowledge. Spyware can get into a computer when the user downloads software from the Internet. Spyware can search the contents of a hard disk, address book of an e-mail, or any information about the computer, and transmits the information to the advertisers or other interested parties.

Answer B is incorrect. A virus is a malicious program that passes from one computer to another in the same way as a biological virus passes from one person to another. Most viruses are written with a malicious intent, so that they may cause damage to programs and data in addition to spreading themselves. Viruses infect existing programs to alter the behavior of programs, actively destroy data, and perform actions to storage devices that render their stored data inaccessible.

Answer A is incorrect. Worms are programs that replicate themselves from one system to another without using a host file. Although in most cases worms exist inside files, such as Word or Excel documents, there is a difference between how worms and viruses use the host file. Usually, a worm releases a document that already has a macro containing a worm inside the document.

Answer D is incorrect. Adware is software that automatically downloads and display advertisements in the Web browser without user permission. When a user visits a site or downloads software, sometimes a hidden adware software is also downloaded to display advertisement automatically. This can be quite irritating to user. Some adware can also be spyware.