Show HN: PII-hound – A fast, dependency-free PII scanner in Go

Show HN: PII-hound – A fast, dependency-free PII scanner in Go(github.com)

4 points by dbuckman 48 days ago | 5 comments

dbuckman 48 days ago |

Hi HN,

I’ve spent a lot of time working on data pipelines, and one of the most frustrating problems is accidentally syncing PII or developer secrets (like AWS keys or SSNs) into a data warehouse or downstream system.

Most of the enterprise tools that solve this are either massive Java applications, require complex Python environments, or cost $50k/year. I just wanted a lightning-fast, single binary I could drop into a CI/CD pipeline (--fail-on-pii) or run locally against a Postgres DB to see my exposure. So, I built pii-hound.

A few technical details on how it works under the hood:

Memory Efficiency: Scanning a 50GB CSV file shouldn't cause an OOM error. It uses a concurrent, streaming architecture and implements Reservoir Sampling so it can sample huge datasets sequentially while maintaining randomness and a tiny memory footprint.

Speed: For the keyword and column-name heuristics, I implemented Aho-Corasick string matching, which is significantly faster than running dozens of individual regexes against every header.

Accuracy: To cut down on false positives, things like Credit Card numbers don't just use regex; they are piped through a Luhn algorithm validation step.

Full transparency: I originally wrote the core of this scanning engine for a larger data management platform I’m building called Saddle Data. But I realized the scanner itself is incredibly useful as a standalone utility, so I extracted it, polished the CLI, and open-sourced it under the MIT license.

It currently supports Postgres, MySQL, Snowflake, BigQuery, SQLite, S3, GCS, and local files (CSV/JSON/Parquet).

I'd love for you to point it at a local database or a messy CSV and let me know how it performs. Happy to answer any questions about the Go implementation, and PRs for new regex rules or source connectors are very welcome!

Finnoid 48 days ago |

Interesting! I notice you mention phone numbers but not names. Can PII-hound also detect things like first and last names in the data? I know that might not be the use case you’re primarily solving for but I’m finding as organizations use AI to process data it’s becoming more important to be able to scrub it from including any PII that might involve user or customer names. I’d love a lightweight CLI tool to do that for me.

dbuckman 48 days ago | |

That is a good question. No, we don't do anything with names at the moment. Names are hard because they don't follow a pattern. The next version will flag columns named first_name, last_name, fullname, or customer_name. That should be published later today.

Beyond that, pii-hound supports custom rules. A user could create some rules to match known names if they wanted.

I am open to ideas of other ways to close that gap.

Finnoid 48 days ago | | |

I don’t know if this is viable but I wonder if you could package a small open source LLM and feed the data through it in chunks to scrub names. I’m sure it would add to the processing time and bunch other issues. But just a thought.

dbuckman 47 days ago |

I have updated pii-hound to include GitHub Actions (SARIF) report and have published a GitHub Action to make pii-hound easy to use in your CI/CD workflows.