All Virus's are ment to do is infect your computer. It is their mission to mess up your pc e.g delete, edit, rename files, mess up system settings etc.
The people who create them try to make it undeleteable so they will make it duplicate itself and place it all over your computer. So what happens is you AV will delete it, but there will be another one on your pc somewhere else. So it will carry on duplicating itself.
Hope this make sense
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