Unfortunately, yes. However, any currency, digital or Fiat, can be and probably is used by criminals. In February 2011, a website was launched called Silk Road run by Dread Pirate Roberts (not his real name). The site was shut down by the FBI in October 2013. In November 2014, the FBI shut down another website called Silk Road 2.0. On both websites, you could only use Bitcoin to transact.