If you're seriously suggesting hacking someone's computer to steal their private keys, well, that's an exceptionally bad idea.  It's a felony under the Computer Fraud and Abuse Act (CFAA) and can land you in federal prison if you're subject to US jurisdiction (and most other countries have similar laws). Cryptocurrencies may seem like a wild west, but there are more than enough laws on the book to punish cyber-criminals.  The government is slow-moving, but it is gearing up on cryptocurrencies, and soon enough you'll start to see prosecutions of hackers who steal Bitcoin.