In some cases, two conflicting global masking policies apply to a single data source. When this happens, the policy containing a tag deeper in the hierarchy will apply to the data source to resolve the conflict.
Consider the following global data policies created by a data governor:
Data policy 1:
Mask columns tagged
PIIby making null for everyone on data sources with columns taggedPII
Data policy 2:
Mask columns tagged
PII.SSNusing hashing for everyone on data sources with columns taggedPII.SSN
If a data owner creates a data source and applies the PII.SSN tag to a column, both of these global masking policies will apply to the column with that tag. Instead of having a conflict, the policy containing a deeper tag in the hierarchy will apply.
In this example, data policy 2 will be applied to the data source because PII.SSN is deeper and thus considered more specific than PII. If data owners wanted to use data policy 1 on the data source instead, they would need to disable data policy 2.
Should two or more masking policies target the same column and have the same hierarchy depth, the policy that was authored first will win out. This is a conservative approach that avoids the original policy being changed unexpectedly.
Similar to masking policies, it is possible for two or more row-level policies to target the same table. When this occurs, all row-level policies will be applied and AND'ed together, meaning the user will need to meet all in some capacity to see any rows in the table at all.
To OR separate row-level policies together, build them into a single Immuta policy together with an OR.
When masking columns, the type of the column matters. For example, it is not possible to hash a numeric column, because the hash would render the number as a string.
Many data platforms make the user account for this by building separate data policies for every column type that could exist now or in the future, which is quite onerous.
Instead, Immuta has intelligent fallbacks. An intelligent fallback occurs when a masking type targets a column type that is incompatible with the masking type. In this case, Immuta will fall back to the most appropriate masking type which retains the level of privacy or better required by the previous type.
For example, if a hashing masking type hits a numeric type, it would intelligently fallback to nulling the column instead, since nulls are allowed in numeric types.
Sometimes a global data policy will target a table and the policy cannot be applied as written. This can happen for several reasons, but the most common is that the row-level policy logic is not relevant to the table in question.
For example, with the following policy
@attributeValuesContains('Attribute Name', 'SOME_COLUMN')
If SOME_COLUMN does not exist in the table, the row-level policy will not work (this is why it is always recommended to use the @columnTagged('tag name') function instead of hard coding column names).
In the case where an error such as this occurs with a global data policy, the lockout policy will kick in. The lockout policy is a row-level policy that blocks any rows from returning for any users. This may seem extreme, but since Immuta does not know how to apply the policy, the lockout policy avoids data leaks until the policy is edited to work correctly.