The IBAN (International Bank Account Number) is a standardized format for uniquely identifying bank accounts in international payments. It consists of a country code, check digits, and the bank identifier plus account number. In an ISMS context, the IBAN is sensitive information: it falls under personal data and can be misused for social engineering attacks or fraudulent transfers. Your classification scheme should define how IBANs are stored, transmitted, and deleted. In emails and documents, only transmit IBANs in plain text when the channel is adequately protected.