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The Data Loss Prevention detector finds sensitive data — PII and secrets — in prompts and model output, and can mask it in flight. Create and configure it in the console under Detectors; attach it from a policy to choose what happens when it matches. It is the only mutable detector: the only one that supports the Transform action (mask matched values before the payload continues). JSON bodies are masked structurally (string values only — keys are never touched); plain-text bodies are masked directly. Matches that are secrets (API keys, access tokens, JWTs, Stripe keys) are reported as secret findings; other entities as PII.

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What it protects against

Three different problems, and they are worth separating because each wants a different action:
  • Personal data leaving your control — reaching a third-party model provider in a prompt. Input + Transform: the request still goes through, masked.
  • Personal data reaching a person who should not see it — regurgitated in an answer. Output + Transform.
  • Credentials leaking — API keys, access tokens, JWTs, Stripe keys. Block rather than Transform: a masked credential has still left, and a request carrying one is usually a bug worth surfacing rather than cleaning.

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Configure

  1. Open Detectors → create a detector and pick Data Loss Prevention.
  2. Under Data Categories, choose what to detect (or use Enable all).
  3. Optionally add Custom rules for keywords or regex patterns that are not in the built-in catalog.
  4. Save the detector, then add it to a policy rule (Input and/or Output) with an action.
You must configure at least one of: Enable all, one or more data categories, or one or more custom rules.

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What happens when it matches

The detector only finds and (when Transform is selected) masks. The action is set on the policy rule that references it:

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Data Categories

The form groups 67 built-in entities into six searchable categories. Toggle them individually, use Search categories to narrow the list, or Enable all to mask every entity at once.

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Personal information

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Financial data

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Secrets & credentials

Every entity here except UUID is reported as a secret finding rather than PII. See Secrets are a different kind of finding.

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Device & network

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Health & medical

Several of these verify a check digit rather than matching a shape, so they produce far fewer false positives than a bare pattern would.

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National & government IDs

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Secrets are a different kind of finding

A leaked credential is an incident, not a privacy problem, and TrustGuard keeps them apart: 22 of the 23 entities in Secrets & credentials are reported as secret findings instead of PII. UUID is the exception — it sits in that group for convenience but is reported as PII, because a UUID on its own is rarely a credential. That split is why secrets usually deserve their own policy rule: Block on them, while everything else is merely masked. When Transform runs, predefined entities are replaced with an entity-specific token (for example [MASKED_EMAIL]) unless you rely only on custom rules.

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Custom rules

Use Custom rules when you need patterns that are not in the built-in catalog — internal account IDs, project codes, product-specific tokens, and so on.
  1. In the detector form, open Custom rules.
  2. Click Add custom rule.
  3. Set Type:
    • Keyword — exact substring match (e.g. confidential).
    • Regex — a regular-expression pattern (e.g. ACME-\d{6}).
  4. Enter the keyword or pattern (required).
  5. Optionally set Mask with (default ***) and Preserve length (replace with * repeated to the original length).
  6. Add more rules as needed; each rule is evaluated in order along with the selected data categories.
Empty patterns are invalid — the console blocks save until every custom rule has a non-empty keyword or regex.

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When to use

  • Output + Transform — strip PII the model regurgitates before it reaches the user.
  • Input + Transform — keep PII out of third-party model providers.
  • Block on the Secrets & credentials group — a masked credential has still left your perimeter, so cleaning it up is not enough.
  • Start with Monitor (and policy Report mode) when enabling broad categories, then switch to Enforce + Block/Transform once the signal looks right.