How are virus produced?

Trojan horse are created by individuals who desire to trigger harm to others, or who desire to get control over someone else's computer.  https://geogenes.org/?p=480 The most basic method to develop a virus is to take some existing code and modify it slightly. This new code can then be dispersed to others, who might unsuspectingly run it on their own computers. As soon as the infection is running, it can do anything its developer desires it to, consisting of erasing files, stealing information, or sending out spam. More advanced viruses can be very hard to eliminate and spot.