because it does or whatever
computer viruses, worms, Trojan horses, and rootkits
In computing, a Trojan horse or just a Trojan is malware that appears to do something good, but usually illegally steals data from your computer (often secretly) for profit.
Malware do not download
"Trojan Horse" does not refer to a specific computer virus, rather it refers to a particular characteristic of some computer malware. A Trojan Horse or Trojan is a bit of software that masquerades as legitimate software but contains hidden malware. It takes its name from the Greek tale from the Trojan War where the Greeks left a big wooden horse outside the gates of Troy with a bunch of Greek soldiers hidden inside. Just like the Greeks used their "Trojan Horse" to trick the Trojans into bringing them inside their defenses, Trojan malware tries to trick users into bringing the malware inside their computer defenses where it can then do its dirty work - such as (but not limited to) data theft, installing backdoors, turning the user's computer into a zombie in a botnet, trashing the computer. Since "Trojan Horse" only refers to a characteristic and not a specific virus, it is impossible to assign an actual date or perpetrator to it. It should also be understood that a Trojan is not really a virus. A virus replicates itself without user intervention, whereas a Trojan relies on tricking a user into downloading it. According to a survey conducted by BitDefender from January to June 2009, "Trojan-type malware is on the rise, accounting for 83-percent of the global malware detected in the world".
A trojan horse virus could cause you to lose sensitive information on your computer, or allow your computer to be controlled remotely by the attacker. It is recommended to always have an anti-virus and anti-malware program installed on your computer to avoid complications from spyware, malware, and viruses.
malware
This can be known by many names. "Malware" is generally used to describe any software that damages your computer. A "Trojan horse" is a specific type of malware which poses as a useful application, but actually performs malicious acts once installed.
Trojan is a kind of Malware. And Malwares are virus.
Worms: A computer worm is a self-replicating malware computer program.Trojan: A Trojan, is malware that appears to perform a desirable function for the user prior to run or install but instead facilitates unauthorized access of the user's computer system.
Actually they aren't. Computer viruses and Trojan horses are two different types of malware, i.e., malicious software.The type known as "Trojan horses" are named after the horse which, according to legend, was given as a "gift" by the Greeks, to the Trojans - their enemies. Just like the horse in the legend, the malware called "Trojan horses" also have a malicious intention. For more information about the legend, check the Wikipedia article on "Trojan horse".
A Trojan Horse.
Trojan Horse