If you learn and implement all of the security measures, bitcoin is very secure (compared to fiat money). First, it is cryptography, meaning that it is secured by mathematical algorithms that cannot be broken even by the most powerful computers. The only danger that bitcoin can fase is the scams and phishing mechanisms that exist in the market (like computer viruses). To avoid them, the users need to select reliable digital wallets, public and private keys, as well as not share confidential information with any other user. Also, they should avoid operations with unknown and strange ICOs, users, exchanges and pools. Otherwise, bitcoin is very secure!