Firewall Rules with nftables - Paranoid Level Sandboxing #5
Source: YouTube · Data Lab Tech · published Aug 18, 2026 · 19:40
This video demonstrates how to implement NFtables firewall rules for Podman networks to sandbox containers—particularly AI agents—by enforcing a deny-by-default policy on a rootful bridge interface 0:00.
Key Takeaways:
• NFtables is the default firewall backend for modern Podman versions, but implementing network-level filtering requires rootful Podman so a bridge interface (e.g., podman1) is created on the host 0:10.
• Rootless Podman does not expose a network interface to the host, making it impractical to filter container traffic with NFtables at this time 4:21.
• The firewall uses an inet (IPv4/IPv6) table with three chains (input, forward, output) where IPv6 is blocked entirely, and the final rule in the forward chain drops all traffic on the Podman interface, creating a deny-by-default stance for containers 7:24.
• Dynamic allowlist rules are generated by resolving domain names to IPs at load time and injecting them into the forward chain before the catch-all drop rule, giving containers controlled access to external services like APIs 13:25.
While the approach is not yet packaged as a user-friendly tool, it provides a practical foundation for adding network-layer sandboxing to untrusted workloads like AI agents.
Sources:
- 0:00 Introduction to NFtables as the standard firewall solution for Podman
- 0:10 NFtables as default in Podman 5+ and rootful requirement
- 4:21 Demonstrating that rootless Podman doesn't create a filterable host interface
- 7:24 Base NFtables rules: table structure, chains, IPv6 blocking, and deny-by-default drop
- 13:25 Dynamic whitelist rule generation via DNS resolution and rule reloading
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First 800 characters of the transcript
What's up guys? So, today we're going to talk about how to implement a firewall rules for your Podman networks, okay? We are going to use NFtables for this, which is, I believe, the standard solution that Podman 6 is adopting. It's already the default in Podman 5 something, I believe. So, it should work out of the box. Make sure that you have NFtables installed and enabled on your Linux distro for this to work. I will show you how what exactly you need to do to be able to set firewall rules for your Podman network. This only works with rootful Podman, so it doesn't really work with rootless as far as I know. And I will show you some basic rule definition with what we've designed for great. Okay, let's get into it. So, we're going to talk NFtables. We're going to create a table called inet …