Some may assume that a keygen and virus are two the same things but they are different from each other. When your computer has a virus, this will have the ability to wipe out all of the things that you have saved on your computer. Having a backup file is important especially if you do not want to lose the files that you have saved.
The keygen is normally used by people who would like to generate some codes for the programs that they want to use but they have not purchased. Some of the keys that will be generated will be enough to make the software or the program work properly. The keygen is not exactly malicious but it is not too honest either.