Trendy online-only Brit bank Monzo is telling hundreds of thousands of its customers to pick a new PIN – after it discovered it was storing their codes as plain-text in log files.
As a result, 480,000 folks, a fifth of the bank’s customers, now have to go to a cash machine, and reset their PINs.
The bank said the numbers, normally tightly secured with extremely limited access, had accidentally been kept in an encrypted-at-rest log file. The content of those logs were, however, accessible to roughly 100 Monzo engineers who normally would not have the clearance nor any need to see customer PINs.
The PINs were logged for punters who had used the “card number reminder” and “cancel a standing order” features.
To hear Monzo tell it, the misconfigured logs, along with the PINs, were discovered on Friday evening. By Saturday morning, the UK bank updated its mobile app so that no new PINs were sent to the log collector. On Monday, the last of the logged data had been deleted.