Credit card numbers are not a random sequence of digits; they are constructed based on ISO 7812, a numbering system, by the International Organization for Standardization, that governs the magnetic stripe cards including credit cards. According to information from CardBenefit, a credit card number contains a major industry identifier, an issuer identification number, an account number and a single-digit check number used to prevent card fraud. An issuer identification number is especially helpful to online merchants in discerning potential credit card frauds. Aside from card network authorisation, bank verification provides another method to ensure an Internet transaction is legitimate.
Pull out a credit card and find the major industry identifier at the beginning of the card number. For example, all Visa card numbers start with the digit 4, which represents the banking and financial industry. The MasterCard network identifies itself with a 2-number sequence that lies between 51 and 55, in which the number 5 also represents the banking and financial industry.
Write down the numbers after the industry identifier until the 6th digit and determine the issuer identification number. While Discover Card and American Express issue their own cards, numerous banks and finance companies issue the same Visa and MasterCard. The industry uses issuer identification numbers to identify different issuing banks. For Visa, digits 2 through 6 are the issuing bank's identification number. For MasterCard, digits 3 through 6 are the issuing bank's identification number.
Enter the issuer identification number into the bank identification database and locate the issuing bank. By ISO rules, the major industry identifier is used along with the issuer identification number to form the so-called card prefix, which is the actual data maintained in a bank identification database. One such database is the Bank Identification Numbers Database from BINBase. For Visa and MasterCard, enter the first 6 card numbers into the database, the search result will show information including bank name, card type and issuer phone number.
The Discover network uses number 6011 for its card identification, of which the number 6 refers to the industry of merchandising and banking. American Express begins with either 34 or 37, in which the number 3 classifies the company as a travel and entertainment entity. For Discover Card and American Express, the card issuers are in most cases the companies themselves. Their respective industry identifier numbers 6011 and 34 or 37 would conveniently self-identify the companies as such a card issuer.