Many spreadsheets store numbers using 16 decimal places of precision, which can match a valid Credit Card number check.
We check all 16 digit numbers that have a leading period or space and end with a period or space or CR. This example number is listed below:
The presence of this number in an email message results in our checking the number, 4012888888881881, which when tested, will verify as a number Visa supports as a CC number. This does not mean it is a credit card number currently in use, but that it passes what is known as the luhn10 test.
If you are sending spreadsheets as an attachment, you can set your program to save numbers to 10 or fewer places or save your document in a password protected archive so it cannot be scanned by the Barracuda for content.
False positives for Credit Card numbers, although rare, do happen but with a little forethought, can be avoided.
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