nullcipher

US Social Security numbers

AAA-GG-SSSS outside the ranges SSA never assigns. There is no check digit, so it is masked only after a context word. Below: the exact rule, a live check, why it matters, and what to do if one already leaked.

Live check: US Social Security number

What an AI chat would receive after masking

SSN [SSN_1]

1 × US Social Security number found and masked.

How the number is built and checked

An SSN is nine digits in three parts: a three-digit area number, a two-digit group number and a four-digit serial number, written AAA-GG-SSSS. [1]

Since 25 June 2011 SSA assigns numbers at random. That ended the geographical meaning of the area number (it used to follow the state) and the use of the highest group number for validation. Randomization excludes the area numbers 000, 666 and 900–999, and never assigns group 00 or serial 0000; numbers with those remain invalid. [1]

An SSN has no check digit. Any nine digits outside those ranges could be someone's number, and a part number such as 123-45-6789 has the same shape. So nullcipher masks one only when SSN, Social Security or soc sec stands within 40 characters before it.

How nullcipher recognises it

AAA-GG-SSSS, AAA GG SSSS or nine digits, where the area AAA is not 000, 666 or 900–999, the group GG is not 00 and the serial SSSS is not 0000 — the numbers the Social Security Administration never assigns. There is no check digit, so it is only masked with a context word — SSN, Social Security, soc sec — within 40 characters before it.

This is the rule text of the “US Social Security number” detector in the masking engine, copied from the engine when this page was built. Detectors run in a fixed order and, where two overlap, the earlier one wins.

Example (fake)

SSN 123-45-6789

nullcipher replaces it with [SSN_1]. Constructed for illustration. Area 123, group 45 and serial 6789 are all in the ranges SSA assigns, which is why nullcipher masks it after “SSN”; there is no check digit that could tell a real number from this one.

Why it matters in an AI chat

SSA's own leaflet says scammers use an SSN to get other information about you and to apply for credit in your name; you may not find out until you are turned down for credit or creditors call about things you never bought.

SSA asks you to be careful about sharing the number even when asked for it, and to ask why it is needed. A pasted onboarding form, a tax document or a support log sends it to a chat provider without anyone having asked.

Masked, the AI sees [SSN_1] and can still help with the form or the log.

If it already leaked

  1. If someone has misused your SSN, report it at IdentityTheft.gov, the Federal Trade Commission's site, which gives you a recovery plan (or call 1-877-438-4338). [2]
  2. Scammers may file a tax return with your SSN to take your refund, or use it to work: if you think that happened, contact the IRS identity protection service (1-800-908-4490). [2]
  3. Check your credit reports regularly; they are free at annualcreditreport.com. If you suspect someone is using your number for work, report it to SSA, which will review your earnings record with you. [2]
  4. A new SSN is a last resort: SSA may assign one if you have done all you can and someone is still using your number, not merely because a card was lost. It warns that a new number does not guarantee a fresh start, and that a number with no credit history can make credit harder to get. [2]
  5. If it only went into an AI chat and there is no sign of misuse, delete the conversation — how, for each major assistant, is on the page listing every type. The number itself stays the same, so the steps above are about noticing and blocking misuse, not about replacing it.

Sources

  1. Social Security Number Randomization — Frequently Asked Questions — Social Security Administration — checked 2026-09-23. ssa.gov refused automated requests on 2026-09-23 (HTTP 403), so the text was checked that day against the Internet Archive's copy captured 2026-08-28. Internet Archive copy, captured 2026-08-28.
  2. Identity Theft and Your Social Security Number (Publication No. 05-10064) — Social Security Administration — checked 2026-09-23. Checked on 2026-09-23 against the Internet Archive's copy captured 2026-09-18, for the same reason. Internet Archive copy, captured 2026-09-18.

Open the full masking tool to mask a whole log, .env file or e-mail — every type at once — and restore the values in the AI's answer. Or see all 30 secret types and how to delete a chat you already sent.