Social Security Numbers (SSN)

Filter

This filter identifies values in the form of US Social Security Numbers (SSN), such as 123-45-6789, 123 45 6789, and 123456789, and reports them with the span type ssn. It does not report values that cannot be SSNs: an area number (the first three digits) of 000, 666, or 9NN, a group number (the middle two digits) of 00, or a serial number (the last four digits) of 0000.

Detection is based on the format of the value. A nine-digit number that is not an SSN, such as an account number, can be reported, and an SSN written in a form the filter does not accept is not. Validate the results against your own documents.

ITINs. A value in the SSN format that begins with 9 is an Individual Taxpayer Identification Number (ITIN), and this filter never reports it. Enable the ITIN filter to detect ITINs.

The EIN format. This filter does not report values in the form NN-NNNNNNN, two digits, a hyphen, and seven digits, which is the form of an Employer Identification Number (EIN). Enable the EIN filter to detect them.

Canadian SINs. An unformatted nine-digit value can match both this filter and the Canadian SIN filter when both are enabled. It is then reported as one of the two types, ssn or canada-sin, and which one is not fixed. If that matters, give both filters the same strategy, or enable only the one you need. Hyphenated values do not collide, since an SSN is grouped NNN-NN-NNNN and a SIN NNN-NNN-NNN.

Separators and line breaks

Between digit groups the filter accepts a hyphen, a single space or other horizontal whitespace character, or nothing at all. In place of the ASCII hyphen it also accepts the soft hyphen (U+00AD), the dashes U+2010 through U+2015, the minus sign (U+2212), and the small and fullwidth hyphen-minus forms (U+FE58, U+FE63, U+FF0D). A value wrapped across a line break is detected when the break follows a hyphen, such as 123-45- at the end of one line followed by 6789 on the next. A match does not begin or end partway through a longer run of digits or letters.

Not detected: digits split across lines with no hyphen before the break, a break inside a digit group, digits outside ASCII (such as fullwidth digits), and more than one whitespace character between groups.

Required Parameters

This filter has no required parameters.

Optional Parameters

Parameter	Description	Default Value
ssnFilterStrategies	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

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, they are evaluated in the order listed and only the first one whose condition is satisfied, or that has no condition, is applied. 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.	< , <=, > , >=, ==, !=

Example Policy

{
   "identifiers": {
      "ssn": {
         "ssnFilterStrategies": [
            {
               "strategy": "REDACT",
               "redactionFormat": "{{{REDACTED-%t}}}"
            }
         ]
      }
   }
}