Little Snitch for Linux
Little Snitch is macOS-only — there is no Linux build. On Linux the real application firewalls are OpenSnitch and Portmaster, both free and open source. This is an honest comparison of them — and where NetInsightPro fits: the cross-platform AI-agent, MCP and fleet layer neither of them has.
On a Mac? This page is for Linux. On macOS, use Little Snitch itself, or the free, open-source LuLu — NetInsightPro has no macOS per-app blocking today.
Also on Windows? See Little Snitch for Windows & Linux: 5 real options compared.
The real Linux options: OpenSnitch & Portmaster
If you came looking for Little Snitch on Linux, these two free, open-source firewalls are what you actually want for per-app control on a single machine. NetInsightPro is not trying to replace them — see the comparison below for exactly where it fits.
OpenSnitch
The Linux answer to Little Snitch’s interactive prompts: a free, open-source application firewall that asks, per app and per connection, whether to allow outbound traffic and remembers your rules. If you want hands-on, per-process control on Linux, start here.
Portmaster
A free, open-source firewall from Safing for Linux and Windows that combines per-app rules with system-wide DNS filtering and a polished UI. A strong choice if you want per-app control plus DNS-level blocking of trackers and ad domains in one tool.
OpenSnitch, Portmaster & NetInsightPro, side by side
A fair read for a Linux user. OpenSnitch and Portmaster are free and open source, and for the base firewall function they block more granularly than NetInsightPro (per app / per connection, versus NetInsightPro’s per-host blocking). NetInsightPro earns its place on platform breadth and the AI/MCP/fleet layer — not on being a cheaper or more granular firewall.
| Product | Platforms | Per-app egress visibility | Blocking granularity | AI-agent / MCP + fleet | Price | Open source |
|---|---|---|---|---|---|---|
| Little Snitch | macOS only — no Linux build | Yes — per app (macOS) | Per-app / per-connection rules | No | €59 one-time | No (proprietary) |
| OpenSnitch | Linux | Yes — per app | Per-app / per-connection prompts | No | Free | Yes — open source |
| Portmaster | Linux, Windows | Yes — per app | Per-app + DNS filtering | No | Free | Yes — open source |
| NetInsightPro | Linux, Windows, Android | Yes — per app (visibility) | Per destination host (OS-firewall-enforced) — not per app | Yes — AI-agent + MCP discovery, fleet console | Free; Pro £12/mo (£100/yr) | No (proprietary) |
Platforms and pricing as at September 2026 — verify current details with each project. OpenSnitch and Portmaster details per each project’s own site; Little Snitch pricing via third-party review sources.
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Cross-platform AI-agent & MCP visibility, with a fleet console
Developers now run Claude Desktop, Cursor and Copilot, and install MCP servers and tools in seconds — often with filesystem or shell access, appearing in no asset register. OpenSnitch and Portmaster are excellent per-app firewalls; what they don’t do is discover AI agents and MCP servers or give you a cross-platform fleet inventory with evidence-based risk and one-click blocking across Linux and Windows hosts — which is what NetInsightPro adds.
Discover AI agents & MCP servers
Find the AI agents and MCP (Model Context Protocol) servers and tools running across your Linux, Windows and Android devices — including native and CLI tools that browser-based controls never see.
Fleet inventory
One inventory of what is running where — ownership, status and last-seen — across a whole fleet of Linux and Windows machines, so shadow AI and MCP supply-chain risk stop hiding in the gaps between hosts.
Evidence-based risk scoring
Risk levels from Low to Critical with the evidence behind each verdict and drill-down. Vulnerability scanning is included and rolling out — today’s scoring is heuristic and evidence-backed, not deep per-package CVE analysis.
One-click block
Block or quarantine a risky agent, MCP server or destination in one click, with an audit trail. A per-app firewall shows you connections; this is the layer that tells you which of them are AI, across every host, and lets you act on it centrally.
We’re early to this category and honest about the edges: for deep per-server static analysis of an MCP server, a code-level scanner goes further, and NetInsightPro complements — not replaces — it. What NetInsightPro gives you that a per-app firewall cannot is fleet-wide endpoint discovery of what’s actually running, and one place to act on it. See how to discover MCP servers & AI agents on your fleet.
What we won’t claim
A comparison you can trust says where it loses. Here is exactly what NetInsightPro does not do on Linux, so you can decide with clear eyes.
On Linux, OpenSnitch and Portmaster are genuinely good and completely free and open source. If you want per-app, per-connection control on a single machine, use one of them — NetInsightPro is not a cheaper or more granular firewall.
NetInsightPro blocks per destination host, enforced through the operating-system firewall — not per app process, and not by killing a live connection. OpenSnitch and Portmaster do per-app rule prompts; NetInsightPro does not.
NetInsightPro is proprietary, not open source. Its paid edge is the cross-platform AI-agent, MCP-server and fleet layer above the firewall — not the base firewall function itself.
NetInsightPro runs alongside your antivirus, never instead of it, and there is no macOS per-app blocking (a macOS build is in review). On a Mac, use Little Snitch or the free, open-source LuLu.
Frequently asked questions
See what your apps connect to — on Linux, Windows & Android
Start free on up to two devices, or go Pro for the AI-agent, MCP and fleet layer OpenSnitch and Portmaster don’t have. Runs alongside your antivirus. Data stays on-device.
Curious about the AI/MCP layer? Explore AI-agent & MCP security or read the MCP discovery guide.