Before sending logs to an LLM, remove or replace credentials, personal data and anything else the analysis does not need. Keep the structure and relationships, such as which host talked to which, by swapping values for consistent tokens. Check your provider's data terms as well, because redaction is only one layer.
Why logs are risky to share
Logs record what really happened, including mistakes. Passwords end up in URLs. API keys appear in command lines. Usernames, email addresses and IP addresses show up everywhere. OWASP's guidance on sensitive information disclosure lists personal data, financial details, health records, confidential business data and security credentials among the things models and applications can expose.
It also notes that users may unknowingly submit sensitive data that the model later reveals, which is why you control the input side.
Redact first
These almost never help the analysis:
- Passwords, tokens, API keys, session cookies and private keys.
- Authorization headers and query strings that carry secrets.
- Full card numbers, national identifiers and health data.
- Message bodies from mail or chat logs, unless the task is about the content.
Detect them with pattern matching before the text leaves your systems. OWASP lists tokenization and redaction with pattern matching as a mitigation.
Tokenize the rest
Some identifiers matter for the story but not for their real value. Replace each user, host and address with a stable token such as USER_1 or HOST_4 within one analysis. The model can still see that USER_1 logged in from HOST_4 and then touched HOST_7, and you hold the mapping to translate the answer back.
Keep real values when they are needed for a public lookup, such as a well known file hash or a public IP you plan to check, and decide that case by case.
Trim the volume
Send the relevant window, not the whole day. Less data means less exposure and usually better answers, because there is less noise.
Control where the data goes
Redaction does not replace policy. Decide which model providers are approved, read their data retention and training terms, and prefer options that let you set retention yourself. Apply least privilege to what the model can retrieve from your own stores, as OWASP advises for access controls.
Test the redactor
Run it on a sample of real logs and read the output. Pattern matching misses new formats. Keep a list of tricky examples and rerun it when log formats change.
What redaction cannot do
It cannot fix a prompt that asks the model to reveal data it should not hold, and OWASP is clear that system prompt restrictions on output are only a partial safeguard. Keep the sensitive material out of reach in the first place.
Quick check
Is hashing usernames enough?
It hides the plain value but keeps a stable identifier that can sometimes be reversed by guessing. Use random tokens with a protected mapping for stronger separation.
Do I need to redact for a self-hosted model?
Often yes for secrets, because the model's logs, prompts and caches become new places where they can leak. Redact credentials either way.
Sources
Last reviewed: 19 October 2026.
