OpenSnitch: Finally, Someone’s Watching What Goes Out

Most firewalls on Linux worry about what’s *coming in*. Which makes sense — until something already inside starts quietly sending data out. That’s where **OpenSnitch** comes in. It doesn’t care about shiny dashboards or cloud integration. It cares about one thing: which process is trying to talk to the network, and whether that should even be allowed.

It’s the kind of tool that surprises people the first time they install it. Suddenly, you notice that your terminal, your PDF viewer, maybe even your text editor is reaching out somewhere — not always for a good reason.

OpenSnitch doesn’t block everything. It just asks. *“This binary is trying to connect to that domain. Is that okay?”* And that alone can change how you look at a workstation.

What It Gets Right

– Watches per process, not just by port or protocol. So yes, `curl` gets different treatment than `python`.
– Interactive popups let you allow or deny in the moment, or make rules for next time.
– Rules can be as specific or vague as needed — per app, per domain, per IP, you name it.
– Lightweight. Runs quietly in the background until something fishy happens.
– Logs everything, in JSON, plain enough to read or ship to Graylog or whatever’s around.
– Open-source and alive, not some forgotten fork or half-working hobby project.

Honestly, once it’s up and running, you start to realize how noisy even “quiet” systems are. And that’s useful.

Not a Replacement — a Missing Layer

OpenSnitch isn’t trying to be your IDS or a full endpoint suite. It’s not competing with tools like **Falco** or **Cortex XDR** — it’s working *alongside* them.

Install? Not That Hard

On Debian-based systems, it’s one command away:

“`
sudo apt install opensnitch
“`

Or, if you prefer to build:

“`
git clone https://github.com/evilsocket/opensnitch.git
cd opensnitch && make && sudo make install
“`

Make sure `opensnitchd` is running, launch the GUI, and that’s it. From there, it starts learning — or, rather, *you* start learning what your system’s been up to.

Real-World Uses

– Locking down developer machines in finance or R&D
– Watching what “free” productivity tools try to reach after install
– Teaching junior staff how modern apps really behave
– Detecting silent background syncs or auto-updates
– Letting users set their own policies without touching `iptables`

Final Thought

There’s a lot of noise in Linux security tools — big promises, bigger dependencies. OpenSnitch isn’t part of that crowd. It does one job: ask before something reaches out. That’s it. No telemetry, no cloud backend, no magic. Just a bit of control, exactly where it’s been missing for years.

If you’ve ever wondered *why the heck is that binary connecting to the internet*, this is the tool that helps you stop asking — and start deciding.