Newer strains are now turning up in other programs as well. All of these viruses use another program's internal programming language, which was created to allow users to automate certain tasks within that program. Because of the ease with which these viruses can be created, there are now thousands of them in circulation. Examples of macro viruses include W97M.Melissa, WM.NiceDay and W97M.Groov. A very important distinction from true viruses is that they do not replicate themselves, as viruses do.
Trojans contain malicious code, that, when triggered, cause loss, or even theft, of data.
Trojan is a Trojan. Worms are programs that replicate themselves from system to system without the use of a host file. This is in contrast to viruses, which requires the spreading of an infected host file. Although worms generally exist inside of other files, often Word or Excel documents, there is a difference between how worms and viruses use the host file. The entire document will travel from computer to computer, so the entire document should be considered the worm.