Federal investigators spent years hunting for clues in the 2016 hacking of the Bitfinex cryptocurrency exchange, when thieves stole bitcoin now worth $4.5bn.
In the end, what helped lead them to two suspects was something much more quotidian: a $500 Walmart gift card.
That card and more than a dozen others like it, including for Uber, Hotels.com...
Read more on fnlondon.com