Sadly, the interactive application firewall OpenSnitch have in practice been unmaintained in Debian for a while. A few days ago I decided to do something about it, and today I am happy with the result. This package monitor network traffic going in and out of a Linux machine, and show a popup dialog to the logged in desktop user, asking to approve or deny any new connections. It has proved very valuable in discovering programs calling home, giving me more control of how information leak out of my Linux machine.
So far the new version is only available in Debian experimental, but I plan to upload it to unstable as soon as I know it is working on a few more machines, and make sure the new version make it into the next stable release of Debian. The package freeze is approaching, and it is not a lot of time left. If you read this blog post, I hope you can be one of the testers.
The new version should be using eBPF on architectures where this is working (amd64 and arm64), and fall back to /proc/ probing where the opensnitch-ebpf-modules package is missing (so far only armhf, a unrelated bug blocks building on riscv64 and s390x). Using eBPF should provide more accurate attribution of packages responsible for network traffic for short lived processes, which some times were unavailable in /proc/ when opensnitch tried to probe for information. I have limited experience with the new version, having used it myself for a day or so. It is easily backportable to Debian 12 Bookworm without code changes, all it need is a simple 'debuild' thanks to the optional build dependencies.
Due to a misfeature of llc on armhf, there is no eBPF support available there. I have not investigated the details, nor reported any bug yet, but for some reason -march=bpf is an unknown option on this architecture, causing the build in the ebpf_prog subdirectory build to fail.
The package is maintained under the umbrella of Debian Go team, and you can meet the current maintainers on the #debian-golang and #opensnitch IRC channels on irc.debian.org.
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