I liked Knoppix and promoted it for years, but I never figured out how one copy was showing me popups of bad websites, so I stopped promoting it years ago. I loved it but can never trust it again after what I saw it doing. I've searched for information and found someone else talking about a similar problem in the same timeframe but have found no explanation. I don't know if the problem was with Knoppix or some upstream software such as the web browser, but there was definitely a problem. I understand that software developers want more money, but programming web browsers to randomly show popups is not ethical. I'm sure they got rid of the problem years ago, so I encourage you to try Knoppix on an old computer, because old computers can often work like new if you merely update the operating system, but I would watch for any unusual behavior with Knoppix. A Live USB or DVD such as Knoppix is a good way to start learning about Linux.