A first identity claim and a first attempt to prove password possession are received. As a result of determining that the first attempt to prove password possession is a match to a password in a set of passwords, but that the first identity claim is a mismatch to an identity that corresponds to the password, an authentication process that includes incrementing a counter associated with the password is performed. A second identity claim and a second attempt to prove password possession is received. As a result of determining that the second attempt to prove password possession is a match to the password, an authentication process that includes incrementing the counter associated with the password only if the second identity claim is a mismatch to the first identity claim is performed.