The goal of Content Filter Data Protection (DLP) is to help you discover and solve data leakage problems on your SharePoint servers. There are 10 default data protection policies configured by region. Compared to standard content filtering policies, keywords in the data protection policies are regular expression description strings and not the actual keyword.
For example, IBAN is the description for the regular expression:
[^\w](([A-Z]{2}\d{2}\s?)([A-Za-z0-9]{11,27}|([A-Za-z0-9]{4}\s){3,6}[A-Za-z0-9]{0,3}|([A-Za-z0-9]{4}\s){2}[A-Za-z0-9]{3,4}))[^\w]. Content that contains the string "IBAN" does not trigger this policy. Strings such as "BE68 5390 0754 7034 " will match the regular expression and trigger this policy.
For more information, refer to the Administrator's Guide, "About Regular Expressions."