Amid growing concern about identity theft, a US banking regulator on Thursday detailed several instances of security breaches at banks and previewed new guidelines on when banks must tell the customers about such lapses.

Amy Friend, assistant chief counsel at the Office of the Comptroller of the Currency, said that in one instance, the agency “directed a large bank to improve its employee screening policies” after determining that the bank had “inadvertently permitted a convicted felon, who engaged in identity theft-related crimes” to become an employee.