Credit card fraud is the bane of any business and if you run an online store, its an even bigger threat. In an eCommerce online store situation, you will unlikely take physical possession of the customers credit card to process the transaction. Instead your magento or woo-commerce developed eCommerce store will rely on 3rd party online payment gateways like MyGate, 2checkout, Payfast and others. This protects the privacy of the card owner, and absolves you from being PCI compliant as you are not storing any credit card information

This does not stop you from requesting the customer to email, fax or read out their card number to you telephonically.

Generally these gateways do have checks and filters to identify fraudulent customers or ‘hot-cards’ but still a few slip through.  Knowing and understanding the sequence of credit card numbers helps a great deal in combatting online fraud and stolen credit cards .

The First Digit represents a major industry. The category of the entity that has issued this card.

  • 1 & 2 – are airline issued
  • 3 would be Travel & Entertainment
  • 4 & 5 are Banking and Financial (your most popular)
  • 6 is merchandising and banking
  • 7 would be petroleum (garage cards)
  • 8 is telecommunications
  • 9 is national assignment.

The first 6 digits are the Issuer Identification Number (INN), allowing you to identify the institution that issued the card

  • Visa: 4xxxxx
  • MasterCard: 51xxxx to 55xxxx
  • Discover: 6011xx, 644xxx, 65xxxx
  • Amex: 34xxx, 37xxxx

For example a card that starts with 376211 would be a Singapore Airlines Krisflyer American Express Gold Card or 529962 would be a pre-paid Much-Music MasterCard.

The 7th and following digits, excluding the final digit, would be the individuals account number. Obviously this unique number has virtually unlimited combinations (a trillion possible numbers!)

The final digit is the check-digit or ‘checksum’.
It is used to validate the credit card using the Luhn algorithm.

Don’t worry though! validating a card is not too difficult.

sample credit card number
4417 1234 4578 9113

  • Double every other digit, starting from the right.
    8 2 2 6 10 14 18 2
  • Now add these new digits to the undoubted ones (all double digit numbers are added as a sum of their digits (eg. 14 becomes 1+4)
  • You will now have
    8+4+2+7        +    2+2+6+4    +    1+0+6+1+4+8    +    1+8+1+2+3
  • Your total should be 70

If your final total is divisible by 10, then the credit card number is valid.  If it is not divisible by 10 then the number is invalid, fake or tampered with.

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