Nope...we don't have anything built in that would mimic that type of behavior. However, depending on how many times (s)he failed the login over a 15 or 30 minute period (i.e. over 25 minutes (s)he logs in 14 times but 4 of those times (s)he mistypes the password) the account may be locked according to the settings in your appconfigs. Under those conditions, looking at the account through the admin section would not show the account as "locked" (that's a setting used to manually lock the account as an admin...it sets the Active field in the customer record to 0) because it just sets the locked until DateTime field to a time x minutes in the future (depending on your appconfig settings). Next time it happens, I would manually take a look at the LockedUntil field in the Customer table to see if it's been updated to a time in the future.
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