“It’s really good for you,” Liam Ghershony, 24, told his father.

Unknown to the recipient, the powder was a benzodiazepine, a class of depressants that includes drugs like Xanax, and was delivered in a dose large enough to purposely knock him out. Then, free to use his father’s cellphone, Ghershony tapped through a two-step authorization to hack into a $400,000 cryptocurrency account.