What should I use to see which user requests are leaking PII?

To identify which user requests are leaking PII, the best tool depends on where the leakage happens:

1. If you want to inspect application logs / requests

Use a PII detection / DLP tool that can scan request bodies, headers, and logs for sensitive data.

Common options:

• Cloud DLP: Google Cloud DLP, AWS Macie, Microsoft Purview
• Log monitoring with PII rules: Datadog Sensitive Data Scanner, Splunk with PII patterns, ELK with custom detectors
• Open-source scanners: Microsoft Presidio, scrubadub, Philter

2. If you want to trace requests end-to-end

Use distributed tracing + request logging with redaction:

• OpenTelemetry for request traces
• Add middleware that logs all inbound/outbound requests
• Run a PII scanner on captured payloads
• Ensure logs are sampled and redacted to avoid creating more leaks

3. If you want to detect leaks in code or APIs

Use:

• Static analysis / secret scanning for code paths that serialize user data
• Schema validation to prevent sensitive fields from being returned
• API gateway inspection for outgoing responses

Best practical recommendation

If you’re looking for something to start with:

• Microsoft Presidio for identifying PII in text/payloads
• OpenTelemetry for tracing requests
• A log platform with sensitive data scanning for ongoing monitoring

Important note

If requests are leaking PII, make sure logs are configured to mask or drop sensitive fields immediately, otherwise the monitoring itself can become a privacy risk.

If you want, I can recommend the best option based on your stack, like AWS / GCP / Azure / Python / Node / Java.