You're right to flag this. The default trust model is broken for any environment that isn't a disposable sandbox. The attack surface isn't just a compromised machine, it's also a malicious or hijacked agent itself. If the agent logic gets subverted, that default-permissive network channel is a ready-made pivot.

I run it in a dedicated VM with a host-based firewall only allowing the specific endpoints I need for that project, like a private repo or a local API. The global "Allow Network Access" toggle is too blunt. The better approach is to treat the agent's network like any other app: deny by default, then build a specific allow list.

Have you looked at whether its repo-fetching uses distinct FQDNs from its telemetry or doc fetching? Segmenting those in a firewall policy is the first step.

That VM setup sounds intense for just a coding assistant! It makes sense though, if the agent itself could be hijacked.

> malicious or hijacked agent itself

This is a scary idea I hadn't considered. Does that mean a bad actor could, like, trick the agent into doing something harmful from inside my own machine? 😬

How do you even start setting up a host-based firewall for something like this? Is there a guide you followed?

You're correct about treating the agent's network like any other app. The host-based firewall approach is sound, but the segmentation question is key.

From my analysis, the repo-fetching, telemetry, and doc fetching often share the same underlying API domains. They're differentiated by path, not FQDN. A firewall rule based solely on domain would still permit too much if one service is compromised.

The real first step is mapping the actual egress patterns. I use a local proxy to log all outbound calls from the agent process during a typical session. You'll often find it calls a central `api.cursor.com` or similar for everything. This means path-based segmentation in a firewall is more complex, sometimes requiring deep packet inspection or just accepting the risk of a broad allow rule to that domain.

A simpler containment method is the VM, but with a network namespace that only has route to your specific project resources, like a private git server. This cuts off the agent's ability to call its own central services entirely, which may break features but enforces a true project-only network.

You've hit on the core issue, but I think it's even one layer deeper. The principle of "minimum access for the current task" is fundamentally incompatible with how these agents are architected. They're monolithic services with baked-in capabilities. Even if you could, in theory, restrict its network to only repo fetching for your current project, the model's own internal weights have been trained on a general corpus that assumes a world of context. It will still try to fulfill requests that require external knowledge, and when blocked, its behavior becomes unpredictable, not secure.

This creates a false sense of control. The real problem is the opaque training data and the inability to validate what the model might be prompted to do internally. A network allow list treats the symptom, not the disease. Until we can audit and constrain the model's *intent* at inference time, firewall rules are just playing whack-a-mole with the symptoms of a permissive default trust model.

You're absolutely right about the attack surface, and it's one of those convenience vs. security trade-offs they don't mention in the tutorials. I've been wrestling with this for a while because I actually *need* the repo-fetching for some projects.

My current stopgap is using Cursor's own "Offline Mode" as a killswitch, but that's the blunt instrument you mentioned. I've found that even with "Allow Network Access" off, the agent will sometimes still attempt calls if you've got a certain workflow history cached. It's weird.

What I've settled on, for now, is a simple script that runs when I launch Cursor. It uses `pfctl` on my Mac to drop all outbound traffic from the Cursor helper process unless I explicitly run another script to enable it for a specific task. It's janky, but it gives me that per-session grant you're looking for. I can share the gist if you're on macOS. For Windows/Linux, the principle would be similar with the native firewall, though automating it is a bit more work.

The real bummer is that there's no config file flag for granular permissions, like "allow GitHub but nothing else." We shouldn't have to build this ourselves.

That pfctl script is the way to go until they give us real controls. It's not janky, it's ops.

I do similar on Linux with nftables. Key is you have to match on the full process hierarchy, not just the main PID. The helpers spawn kids.

The cached workflow thing is because it's not a true offline mode. It's a UI toggle, not a network namespace. Your script is fixing their design.

>We shouldn't have to build this ourselves.

Exactly. It's a monitoring nightmare. My prometheus stack can't see the blocked calls unless I pipe the pf logs somewhere. Another layer to manage.

Yeah, that's a really good point about new users. I was one of those people a few months ago, just trusting it because it's a tool for work. The idea that it's calling out constantly without a prompt is kind of unsettling.

> I worry that new users, especially those coming here to learn, might not even realize the traffic is flowing.

This was totally me. I only noticed because my pihole logs were going crazy with `api.cursor.com` while I was just writing local Python scripts. I don't think most tutorials even mention it.

Is there any way to see a log of what it's actually trying to fetch from inside Cursor itself? Like a verbose mode? Or is the only way a network monitor?

>monolithic services with baked-in capabilities

That makes so much sense and feels a bit hopeless. Like, if the training itself makes it expect the world, blocking it might just make it confused and weird, not safe.

Is the only real fix for them to build in some kind of permission prompt? Like, a pop-up asking "Agent wants to fetch from github.com, allow?" for each new domain? That would be annoying but maybe clearer.