Use Bitcoin - Doh!
The hackers behind the massive WannaCry cyberattack are dumb idiots! Their Bitcoin account now reads $66,000 in Bitcoin, but how the hell are they going to move it anywhere? If I were them I'd have asked for Monero. Period.
Converting this amount of Bitcoin to cash will be tough with the whole world watching. They could sell Bitcoin for cash on the darknet markets, but even the NSA etc. are constantly watching there too.
Privacy not assured
The privacy of Bitcoin is not absolute, so once an attempt is made to swap it out to fiat currency the noose will tighten!
The hackers were charging $300 to release files, and only 3 randomly generated addresses were used for the entire attack. This is unbelievable. You can tell they are not yet skilled in blockchain.
By yesterday morning when I looked at the Bitcoin account in question it read 251 transactions with a US dollar value of $66,000. Good luck with moving all that. Try Monero next time. Symbol XMR!