Posted: 9/4/2009, Updated: 6/10/2013
When searching for credit card numbers in Microsoft Excel spreadsheets, it may appear as though Identity Finder is failing to find true positives. Before continuing with the detail below, it is important to ensure that Identity Finder is attempting to search the specified location. If the location is not being searched, no matches will be found.
There is a limitation in the precision of Excel that can prevent matching of certain types of credit card numbers. To view this limitation, perform the following steps.
- Open Microsoft Excel.
- In an empty cell, enter a 16 digit number such as 4111111111111111 and then press enter.
- Move the cursor over the cell used in step 2.
- View the value bar at the top of the Excel window and note that the last digit is a 0 even though a 1 was originally entered.
- Change the last digit to a 2 and hit enter and then move the selection back to that cell and note that it is still a 0.
Because Excel does not have the capacity to store credit card numbers of 16 or more digits, it may appear as though Identity Finder is missing matches; however, this is not the case. Once one or more digits are changed to 0, the number will likely fail the test necessary to flag the item as a valid credit card number.