# filter_nist_rds

The function `filter_nist_rds` calculates the checksum of the file associated with a document. If the checksum is present in a NIST RDS hash set, the function adds the fields `AUTN_NIST_RDS_LIST`, `AUTN_NO_FILTER`, and `AUTN_NO_EXTRACT` to the document.

The NIST RDS hash sets contain the checksums of millions of files that originate from operating systems and application software, so you can use this function to filter out documents that represent those files.

NOTE: Before using this function you must populate a datastore with the NIST RDS hash set(s). For information about how to do this, refer to the CFS Administration Guide.

## Syntax

    filter_nist_rds(document, section)

## Arguments

Argument | Description
--- | ---
`document` | (LuaDocument) The document to check.
`section` | (string) The name of a section in the CFS configuration file that contains the task settings to use.

## Examples

The following example discards any document where the associated file matches an entry in a NIST RDS hash set.

    function handler(document)
        filter_nist_rds(document, "NistRdsFilterSection")
        return not document:hasField("AUTN_NIST_RDS_LIST")
    end

The task might be configured, in the CFS configuration file, as follows.

    [NistRdsFilterSection]
    NistRdsStoreType=BTREE

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