A Fraud Detection rule can incorrectly make a true assessment due to NULL values.
The EXISTS and IS_MISSING operators assess a value as NULL if specified information is not provided.
For example, if you set the rule :billing_address_country: = :shipping_address_country:, but do not provide either address in your payment request, the values that are compared are NULL = NULL, which evaluates to true.
Empty values and white spaces are considered to be different. So when comparing two values that have different white spaces, they are assessed as different even if the text is intended to be the same.