With all the ransomware attacks the FBI and CIA have stepped up their efforts into tracking and tracing illicit bitcoin funds, supposedly they have found a way to reliably track coins but also obtain access to the wallets that store them to recover the funds.
https://hackernoon.com/did-the-fbi-hack-the-bitcoin-yv3235gx
https://hackernoon.com/did-the-fbi-hack-the-bitcoin-yv3235gx