In conventional usage, the term â€œhacking generally refers to an unauthorized user gaining access to an electronic resource. Hackers use various means to steal, guess, calculate, or otherwise obtain credentials to access systems and data they are not allowed to access. When we talk about â€œhacking a blockchain, however, this does not adequately or accurately describe what has happened and blinds us to understanding where the real risks lie in this new technology of distributed ledgers and crypto-assets. The high-profile, most destructive, and expensive â€œhacks in blockchain environments actually represent *authorized* users misbehaving. In some cases, these are authorized users acting on their own behalf to exploit weaknesses in the system to their own gain at the expense of other users, in other cases these are authorized users who are misusing the trust placed in them by their customers. The key to protecting yourself against fraud in this new alien world of blockchains is to become sufficiently acquainted with the technology and its peculiar jargon. This one-hour presentation is by a technologist, to help non-technologists understand and engage with blockchains and cryptocurrencies.