GreenSpot

Malware:

Malware is a harmful/malicious software. It compromises of a number of harmful software that are threats to all computer user. Malware are created for attack on privacy, spying, destruction and financial benefits.

Most common types of malware are:

Computer viruses
Worms
Spyware
Adware

Computer Viruses:

A computer virus is a type of malware that spreads by inserting copy of itself into another program or file

Most of the viruses are attached to executable(.exe ) file.
Viruses spreads and inflect other files when a computer user open the inflected progra or file
Viruses also spread when inflected files are transferred from one computer to another through network, USB flash drive, CD/DVD or inflected e-mail attachments.
Some viruses are not very harmful they are simply annoying while others can seriously damage the hardware, software or the information stored on the computer.
Viruses can slow down the computer and some can even stop its operations.

Example of viruses are I Love You, my Doom, etc. I Love You is an e-mail virus that inflect computer when user opened an e-mail attachment named "I love You" . My doom virus was discovered in 2004. it quickly inflected about one million computers.

Worms:

A worm is a malware that transmit itself over a network to inflect other computers.

worm can be harmful like virus
it spreads automatically in computer network and replicate itself. it can travel from computer to computer without any human action.
it enters a computer through weakness of the operating system of computer.
Most of worms cause some harm to network such as slowing down communication by increasing network traffic.

Code red and Fizzer are example of worms. Code red worm broke out in July, 2001 and inflected 360,000 computers in a single day. Fizzer is a mass mailing worm that captures a user's Keystrokes and can allow the attackers access to inflect computer.

Spyware:

Spyware programs are developed to spy on computer user by gathering information about their activities on the computer.

Spyware are developed for the personal benefits of the Creator.
it performs secret operations such as stealing password of banking PIN (Personal Identification Number) or other personal information about user.
it indicates computer through installation of software from Internet.
it slows down the performance of inflected computer.
mos of the spy ware is designed to be difficult to remove.

For example, Flame is a spyware that discovered in 2012. it attacks computer that use Microsoft windows operating system. it is known as one of the most sophisticated spyware used for purpose of espionage. it records screenshot, keyboard activity and network traffic and record conversation over Skype.