Yes before bitcoin criminal activities are happen but now the activities are happen with the help of Bitcoin. Bitcoin is ban in many country like North Korea, Bangladesh etc for  this reason. Bitcoin provide its user an high-level privacy and uninterrupted money transaction facility due to this many people using this to hide their black money. Some other criminal activities like anti money laundering, kidnapping, childprongraphy.etc. Many anti social people using Bitcoin as a fraud to people.