Malware

Malware is software designed to infiltrate or damage a computer system, server or computer network without permission from the owner.

Malware includes computer viruses, computer worms, Trojan horse (Trojan horses), majority-root kit (rootkits), the surveillance device (spyware), advertising tools (adware) that dishonest, evil device (crimeware) and any other malicious software and unwanted

Malware outbreak: computer viruses and worms
Malware's most recognizable, 'virus' and 'computer worm', known by the way she spread, not the behavior of others. The term 'computer virus' is used for software that has spread some of the software can be like (executable software) and make the software, when executed, spreads the virus to be like any other software. Viruses also can carry a payload (payload) that perform other actions, often malicious. Conversely, 'computer worm' is software that actively deliver himself through a network to infect other computers, and also can carry a payload.

This conception indicates that the virus requires user intervention to spread, while a computer worm can spread automatically. By using these differences, the outbreak of the sent through surel or Microsoft Word documents that depend on the recipient's actions (opening files or surel) to infect the system, should be classified as a virus rather than a computer worm.

Source : www.wikipedia.com