# Using Exclusion Rules

An Exclusion Rule allows you to refine a Detector to make sure false positives are not surfaced by Nightfall.

For instance you may want to detect whether credit card numbers are being shared inappropriately in your organization. However, there may be cases where members of your QA are sharing test credit card numbers, which should not be considered a violation and should be ignored by Nightfall.

In the following example, we define a Detector with a regular expression to match credit cards.

We then add an exclusion for some known test credit cards.

```sh
curl --location --request POST 'https://api.nightfall.ai/v3/scan' \
--header 'Accept: application/json' \
--header 'Authorization: Bearer NF-rEpLaCeM3w1ThYoUrNiGhTfAlLKeY123' \
--header 'Content-Type: application/json' \
--data-raw '{
    "policy": {
        "detectionRules": [
            {
                "detectors": [
                    {
                        "regex": {
                            "pattern": "(?:(4[0-9]{12}(?:[0-9]{3})?)|(5[1-5][0-9]{14})|(6(?:011|5[0-9]{2})[0-9]{12})|(3[47][0-9]{13})|(3(?:0[0-5]|[68][0-9])[0-9]{11})|((?:2131|1800|35[0-9]{3})[0-9]{11}))",
                            "isCaseSensitive": false
                        },
                        "exclusionRules": [
                            {
                                "wordList": {
                                    "values": [
                                        "4111111111111111",
                                        "5105105105105100"
                                    ]
                                },
                                "exclusionType": "WORD_LIST",
                                "matchType": "FULL"
                            }
                        ],
                        "minNumFindings": 1,
                        "minConfidence": "POSSIBLE",
                        "displayName": "Credit Card Reg Ex",
                        "detectorType": "REGEX"
                    }
                ],
                "name": "Credit Card Detection Rule",
                "logicalOp": "ALL"
            }
        ]
    },
    "payload": [
        "5105105105105100",
        "4111111111111111",
        "4012888888881881"
    ]
}'
```

As the resulting payload shows, only the 3rd provided Credit Card number matches because the first two items in the payload are included in our ExclusionRules word list.

```json
{
   "findings":[
      [
         
      ],
      [
         
      ],
      [
         {
            "finding":"4012888888881881",
            "detector":{
               "name":"Credit Card Reg Ex",
               "uuid":"93024e88-e6de-4c84-8295-75157cdd1b52"
            },
            "confidence":"LIKELY",
            "location":{
               "byteRange":{
                  "start":0,
                  "end":16
               },
               "codepointRange":{
                  "start":0,
                  "end":16
               },
               "rowRange":null,
               "columnRange":null,
               "commitHash":""
            },
            "matchedDetectionRuleUUIDs":[
               
            ],
            "matchedDetectionRules":[
               "Credit Card Detection Rule"
            ]
         }
      ]
   ],
   "redactedPayload":[
      "",
      "",
      ""
   ]
}
```


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