RAG PII Redaction and Sensitive Data Filters

Status: public · Confidence: medium (0.725) · Basis: verified_sources

## TL;DR

RAG systems need sensitive-data filters before indexing, before retrieval, and before answer generation because private text can leak through any of those paths.

## Core Explanation

Retrieval systems often ingest raw documents from tickets, chats, logs, emails, PDFs, CRM records, and source repositories. Those sources can contain names, addresses, keys, account numbers, medical details, or customer identifiers. If sensitive text is embedded and indexed, later prompts can retrieve it even when the original source should not be exposed.

A practical RAG privacy pipeline records which detector ran, which entity types were scanned, which transformation was applied, and whether the original text remains recoverable. It should also preserve enough metadata for audits without putting the sensitive value back into logs or citation snippets.

Agents should treat redaction as a data-processing step with evidence. A retrieval answer should know whether context was raw, masked, tokenized, dropped, or filtered by permission. Otherwise the agent may cite a source that the current user is not allowed to inspect.

## Source-Mapped Facts

- Microsoft Presidio documentation describes Presidio as an SDK for data protection and de-identification that can identify and anonymize private entities in text and images. ([source](https://microsoft.github.io/presidio/))
- Google Sensitive Data Protection documentation says de-identification detects sensitive data such as PII and then masks, deletes, or otherwise obscures it. ([source](https://cloud.google.com/sensitive-data-protection/docs/deidentify-sensitive-data))
- Amazon Comprehend documentation says it can detect PII entities in English or Spanish text documents and can redact PII entities in text. ([source](https://docs.aws.amazon.com/comprehend/latest/dg/how-pii.html))

## Further Reading

- [Microsoft Presidio](https://microsoft.github.io/presidio/)
- [Google Sensitive Data Protection De-identification](https://cloud.google.com/sensitive-data-protection/docs/deidentify-sensitive-data)
- [Amazon Comprehend PII Detection](https://docs.aws.amazon.com/comprehend/latest/dg/how-pii.html)