PII Credit Card and SSN Redaction
This rule watches text flowing through an AI agent for full credit card numbers (Visa, Mastercard, Amex, Discover) and US Social Security Numbers. When it finds one, it redacts everything except the last four digits before the content is shown, stored, or passed along.
How the attack works
Sensitive numbers can end up in AI agent input or output in several ways: a user pastes them into a prompt, a connected tool or document returns them, or the model itself generates or repeats them from context. If this content is not filtered, it can be logged, displayed to unauthorized viewers, sent to downstream systems, or included in exported transcripts. This rule scans content for patterns matching card numbers and SSNs and replaces the sensitive digits with masking, keeping only the last four for reference.
Netzilo detection
Netzilo can block this behaviour when it is observed.
- Signature ID
- netzilo-pii-cc-ssn-redact-001
- Severity
- Critical
Why it matters
Without this kind of check, full card numbers and SSNs can leak into logs, chat transcripts, third-party integrations, or support tickets, creating exposure under PCI-DSS and privacy regulations and giving attackers or careless insiders a direct path to identity theft or fraud.
What you can do
- →Review logs and transcripts that predate this control for stored raw PII and purge or re-redact them.
- →Check the false-positive filter against your own test/documentation data formats so placeholder numbers aren't over-redacted in ways that hide real issues.
- →Restrict who can view unredacted content and any exports or backups that might bypass redaction.
- →Confirm redaction applies consistently to all output paths (UI, logs, API responses, third-party integrations), not just the primary chat interface.
Known benign look-alikes
- Test data with example card numbers (mitigated by filter)
- Documentation with placeholder SSNs