Ethics isn't always black and white. There are some issues that are dubious and it's difficult to know if it's entirely ethical or unethical. Although downloading music might be illegal, I personally don't think it's entirely unethical. On the other hand, a computer virus harms people's computer and prevents them from using it. It can destroy files or give strangers access to the computer. They may steal their personal information and use it.
So we have to realize that ethics is a scale and every unethical action doesn't weigh the same on the scale.