If you use Predefined Filters for Data Leakage Prevention (DLP) and have a problem with the credit card filter taking action (false positives) with spreadsheet files that do NOT contain credit card numbers, this article gives a simple solution. Predefined Filters are configured on the BLOCK/ACCEPT > Content Filtering page in the Predefined Filters section.
Spreadsheets can store numbers to 16 decimal places which can match a valid Credit Card number check. The Barracuda Email Security Gateway checks all 16 digit numbers that have a leading period or space and end with a period or space or <CR>, so this number, for example:
254.4012888888881881
...results in checking the number 4012888888881881 against the credit card filter. When tested, this number verifies as a number pattern Visa supports as a credit card 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 attachments, you should 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 Email Security Gateway for content.