Procedure

1. Go to Data Loss Prevention → Data Identifiers.
2. Click the Expression tab.
3. Click Add.
   A new screen displays.
4. Type an expression name that does not exceed 256 characters in length.
5. Type a description that does not exceed 256 characters in length.
6. Type the displayed data.
   For example, if you are creating an expression for ID numbers, type a sample ID number. This data is used for reference purposes only and will not appear elsewhere in the product.
7. Choose one of the following criteria and configure additional settings for the chosen criteria (see Criteria for Customized Expressions):
   • None
   • Specific characters
   • Suffix
   • Single-character separator
8. Optional: Select a validator for the expression.

   Note Data units follow semantic rules. Not every 9-digit number is a valid social security number and not every 15- or 16-digit number is a valid credit card number. To reduce false positives, expression validators check if the extracted data units follow these rules.

9. Test the expression against an actual data.
   For example, if the expression is for a national ID, type a valid ID number in the Test data text box, click Test, and then check the result.
10. Click Save if you are satisfied with the result.

    Note Save the settings only if the testing was successful. An expression that cannot detect any data wastes system resources and may impact performance.