Driver's License Numbers

Filter

This filter identifies U.S. driver's license numbers in the formats of all 50 states and the District of Columbia.

Many states issue license numbers that are only digits, such as 194784357, which cannot be told apart from a house number, ZIP code, or amount by their shape. A match that contains no letters is identified only when one of these contextual terms appears within windowSize words of it, ignoring case and punctuation: license, licence, lic, driver, drivers, or driver's. DL, D.L., and DLN also count, but only in capitals, because lowercase dl or dL is usually the deciliter unit. For example, 194784357 is identified in Driver's license 194784357 and DL# 194784357 but not in the number is 194784357. A match that contains a letter, such as D1234567, is identified without a contextual term.

Required Parameters

This filter has no required parameters.

Optional Parameters

Parameter	Description	Default Value
driversLicenseFilterStrategies	A list of filter strategies.	None
enabled	When set to false, the filter will be disabled and not applied	true
ignored	A list of terms to be ignored by the filter.	None
windowSize	Sets the size of the window (in terms) surrounding a span to look for contextual terms. An all-digit match is identified only when a contextual term is in this window. If set, this value overrides the value of span.window.size in the configuration.	The value of span.window.size which is by default 5.
priority	The priority (integer) of this filter. Valid values are any positive integer, where a higher value indicates a higher priority. Priority is used for tie-breaking when two spans may be otherwise identical.	0

Filter Strategies

The filter may have zero or more filter strategies. When no filter strategy is given the default strategy of REDACT is used. When multiple filter strategies are given the filter strategies will be applied in order as they are listed. See Filter Strategies for details.

Strategy	Description
REDACT	Replace the sensitive text with a placeholder.
MASK	Replace each character of the sensitive text with a mask character (* by default).
TRUNCATE	Replace all but a few characters of the sensitive text with a truncation character (* by default).
RANDOM_REPLACE	Replace the sensitive text with a similar, random value.
STATIC_REPLACE	Replace the sensitive text with a given value.
CRYPTO_REPLACE	Replace the sensitive text with its encrypted value.
HASH_SHA256_REPLACE	Replace the sensitive text with its SHA256 hash value.
FPE_ENCRYPT_REPLACE	Replace the sensitive text with a value generated by format-preserving encryption (FPE)
LAST_4	Replace the sensitive text with just the last four characters of the text.

Conditions

Each filter strategy may have one condition. See Conditions for details.

Conditional	Description	Operators
TOKEN	Compares the value of the sensitive text.	==, !=, startswith
CONTEXT	Compares the filtering context.	== , !=
CONFIDENCE	Compares the confidence in the sensitive text against a threshold value.	< , <=, > , >=, ==, !=

Limitations

• A contextual term can belong to a different value. The rule checks only that a contextual term is near an all-digit match, not that the term describes it. In Driver's license on file. Address: 1234 Oak Street, the house number 1234 is within the window of license and is redacted as a driver's license number. To avoid this, also enable the street address and ZIP code filters, which identify those values as addresses and ZIP codes instead, or add an ignoredPatterns entry for the shapes to skip, such as \d{4,5}. An ignored pattern must match the whole value, so \d{4,5} does not skip 12345678, but it does skip a real 4 or 5 digit license.
• A label farther away than windowSize words is not seen. On a form where Driver's license is a heading several lines above the number, the number has no contextual term in its window and is not identified. Increase windowSize for such documents, which also lets more unrelated numbers pick up a nearby contextual term.

Example Policy

{
   "identifiers": {
      "driversLicense": {
         "driversLicenseFilterStrategies": [
            {
               "strategy": "REDACT",
               "redactionFormat": "{{{REDACTED-%t}}}"
            }
         ]
      }
   }
}