Firewall & Block Events
The Sielum Firewall lets you cut endpoints off from specific domains. Block rules are enforced at the OS network layer — connections to blocked domains are dropped before any data leaves the endpoint.
A firewall rule is an OS-level rule keyed on the domain's IP addresses. It drops the connection for every process on the endpoint, including the user's own browser and tools that have nothing to do with AI. There is currently no way to scope a block to a single agent.
Use this to ban a prohibited service outright on a device. Do not expect it to isolate one agent while leaving the rest of the machine's network access intact.
Domain rules
Each firewall rule targets one domain (and all its subdomains) and has two switches:
| Field | Meaning |
|---|---|
| Enabled | Whether the rule is distributed to your agents at all |
| Block | Whether the rule is a block rule |
Whether an enabled block rule actually drops traffic is not decided per rule — it depends on the enforcement mode of the endpoint, see below.
Audit vs. enforce is a per-device setting
Every endpoint runs in one of two enforcement modes. The default is audit, which is the safe setting for rollout.
| Mode | Behavior with an enabled block rule |
|---|---|
| Audit (default) | Connection is not blocked; the match is logged as a Block Event |
| Enforce | Connection is dropped at the OS firewall; the Block Event is logged |
Set the mode in Devices: use the audit/enforce toggle on an endpoint row, or select
several endpoints and apply the mode in bulk. The toggle is disabled for endpoints whose
agent is not privileged — enforcement needs CAP_NET_ADMIN (Linux) or administrator rights.
This lets you write one set of rules and roll enforcement out device by device: keep most of the fleet in audit while you check the Block Events, then flip individual endpoints to enforce.
Creating a firewall rule
- Navigate to Firewall in the left sidebar
- Click New Rule
- Enter the target domain (e.g.
api.openai.com) - Optionally add a comment describing why the rule exists
- Click Save — the rule is created disabled
- Enable the rule when you are ready to distribute it
Enabled rules are picked up by each agent on its next check-in — by default every 5 minutes (see Agent Configuration). The agent resolves the domain to IP addresses and installs the corresponding outbound rules. Rules are removed again when the agent shuts down.
Example rules
| Domain | Use case |
|---|---|
api.openai.com | Block direct ChatGPT API access from AI agents |
api.anthropic.com | Block direct Claude API access (not via approved proxy) |
generativelanguage.googleapis.com | Block Gemini API |
copilot.github.com | Block GitHub Copilot completion endpoint |
Block Events
Every time an AI agent's observed connection matches an enabled block rule, a Block Event is recorded — in audit mode as well as in enforce mode. Block Events are visible under Block Events and show:
- Timestamp
- Endpoint hostname
- The process whose connection matched, and its PID
- Destination domain and IP
- Mode (audit / enforce)
The process and PID identify which agent's connection attempt matched the rule. In enforce mode the underlying block is still device-wide, so other processes reaching the same domain are dropped too, without appearing as separate events.
Block Events are preserved for audit purposes even after a rule is deleted or disabled.
How enforcement works
When the agent runs in privileged mode (requires CAP_NET_ADMIN on Linux), firewall rules are enforced via:
- Linux:
iptables(IPv4) andip6tables(IPv6) - macOS:
pf(handles both address families) - Windows: WFP (Windows Filtering Platform)
In user mode the agent cannot install firewall rules at all. Such endpoints stay in audit behavior no matter which mode is selected, and the enforce toggle is disabled for them in the dashboard. See Agent Installation → for details on operating modes.