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Sentry

See which apps on your Mac are talking to the internet, to whom, and in which country

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About Sentry

Sentry is built to watch, passively, which apps on your Mac are talking to the network and where those connections land. It parses lsof output into a per-app breakdown with remote IPs, reverse-DNS hostnames, connection states, and country flags from a bundled MaxMind GeoLite2 database. The design includes 'first seen' alerts for the moment an app reaches a server it has never reached before, a trust system for marking connections or whole apps as expected, and a suspicious flag for known tracker domains. History goes to SQLite with search, filtering and CSV export. It blocks nothing, by design — this is a transparency tool, not a firewall.

Who it's for

Privacy-conscious users who want to see exactly what's phoning home.

What it does

  • Per-app network connection breakdown
  • Country flags via bundled GeoLite2 database
  • Reverse DNS for human-readable hostnames
  • 'First seen' alerts for new connections
  • Trust system: mark connections or apps as Trusted
  • Suspicious flag for known tracker domains
  • Connection history with search, filter, and CSV export

Behind the build

Parsing the MaxMind MMDB binary format in pure Swift was the biggest challenge.

The format uses a search tree of 128-bit nodes for IPv6 prefix lookups — I wrote a zero-dependency reader that traverses the tree and decodes the data section's custom binary format. Reverse DNS runs asynchronously with a cache to avoid blocking the 3-second refresh cycle.

Information

Runs on
macOS · Menu bar
Status
Source only
Requires
macOS 14+
Source
Public on GitHub
Telemetry
None
Built with
Swift & SwiftUI
Stack
SwiftUIProcess/PipeMaxMind MMDBSQLiteActors

Works well with

  • PortMap

    PortMap shows local ports, Sentry shows where they connect to

  • Canary

    Sentry monitors live connections, Canary monitors breach exposure

Sentry is source only, for now.

The code is public, but there's no packaged release yet. Build it from the repository today, or leave an email and hear when there's one you can double-click.

Tell me when it shipsView source

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