Share LinkedIn Twitter Facebook A new study has found that password structure is a key flaw in making login IDs hard to guess. Security firm Praetorian analyzed 34 million stolen passwords from the LinkedIn, eHarmony and Rockyou breaches and found that 50 per cent of all passwords followed 13 basic structures. This lack of entropy makes it possible to use statistical analysis to make cracking faster and more effective. A key part of the problem is with the websites themselves, as they don’t go far enough in prompting user security. Just requiring one upper case letter or number is not good enough when too many users go for the same password structure, as Praetorian explains.