Evaluating a trial deployment of password re-use for phishing prevention

We propose a scheme that exploits scale to prevent phishing. We show that while stopping phishers from obtaining passwords is very hard, detecting the fact that a password has been entered at an unfamiliar site is simple. Our solution involves a client that reports Password Re-Use (PRU) events at unfamiliar sites, and a server that accumulates these reports and detects an attack. We show that it is simple to then mitigate the damage by communicating the identities of phished accounts to the institution under attack. Thus, we make no attempt to prevent information leakage, but we try to detect and then rescue users from the consequences of bad trust decisions.