Hi all,
I built SailHighSea Firewall, a small open-source firewall for Windows that lets you choose which apps are allowed to go online. It's in the spirit of simplewall: default-deny for outbound traffic, and you build an allow-list of the programs you trust.
It talks directly to the Windows Filtering Platform (the same engine Windows Defender Firewall uses). It's written in plain C and Win32, so the whole thing is one ~360 KB .exe with no installer and no runtime. Settings and lists are saved next to the exe, so it's portable.
What it does:
– Default-deny outbound: one button to enable or disable the filters (permanent, or only until reboot, which is handy while testing)
– Per-app allow list, covering IPv4 and IPv6
– Timed allow: let an app online for 15 min up to 8 h, then it's blocked again automatically
– Pop-up when something gets blocked, with Allow / 15 min / Ignore and a countdown
– DNS switch: one button to flip your DNS between automatic and presets (Cloudflare, Google, Quad9, OpenDNS, AdGuard) or your own custom servers; the active one shows in the status bar
– Dark / light / follow-Windows theme, tray icon, start with Windows, row highlighting, search, sortable columns, high-DPI aware
– debug-log.txt next to the exe for bug reports (logs file names only, no full paths or IPs)
– Emergency switch: run it with –disable-filters to remove every filter if you ever lock yourself out
Honest limitations: this is v0.0.1 and very early. It only filters outbound connections, works on executable paths (so Store apps and individual Windows services aren't handled yet), and has no connection log or per-port rules yet. Please try it on a non-critical machine first. A default-deny firewall with a missing rule can cut you off from the network, though Disable Filters always puts things back.
It needs Windows 10/11 64-bit and admin rights. MIT licensed.
Download / source: https://github.com/SailHighSea/sailhighsea-fw
I'd really appreciate bug reports, ideas and criticism, especially from anyone who runs simplewall or similar tools: what would you want it to do next?
Source: r/windowsapps · by /u/SailHighSea