Hi everyone. I've been reading through the forum and trying to follow the discussions on egress controls, especially around proxies. I think I'm getting the basic idea, but I keep getting tripped up on one fundamental thing.
In the context of controlling agent traffic—like for a homelab or a small self-hosted setup—what exactly is the practical difference between a forward proxy and a reverse proxy? I see both mentioned a lot when talking about filtering traffic or setting up security.
I understand a forward proxy (like Squid) sits in front of clients and handles their outbound requests to the internet. It seems like that's for user or agent egress control. A reverse proxy (like nginx or Traefik) sits in front of servers and handles inbound requests from clients. That seems more for protecting services you're hosting.
But when we talk about "layer 7 egress controls," are we always only talking about the forward proxy side of things? Or can a reverse proxy play a role in controlling what traffic *leaves* your internal network? I think I'm confusing the "direction" of control.
If anyone could explain it in terms of these use cases, maybe with a simple example of where you'd place each, I'd be really grateful. Thanks so much for your patience with a beginner question.
Good question! I also got stuck on the "direction" part when I started.
> can a reverse proxy play a role in controlling what traffic *leaves*
For egress control, it's almost always a forward proxy. The client (or agent) is configured to use it when *initiating* calls to the outside. A reverse proxy's job is to handle inbound requests *to* your services, so it doesn't typically filter what leaves your network.
But thinking about agent frameworks, could a reverse proxy be used if the agent itself is the "server" waiting for a callback? Like, the agent pulls tasks, then opens a connection back to command and control? Maybe then the reverse proxy rules could inspect that traffic? Just a thought, I'm still piecing this together myself.
You're circling around an important nuance, but the terminology is getting muddled. The proxy's function is defined by who it's proxying *for*, not just traffic direction.
You asked if a reverse proxy could inspect traffic when an agent acts as a server for a callback. In that specific scenario, the agent's listener *is* an internal service. A reverse proxy placed in front of it *would* inspect inbound traffic *to* that agent, from the C2 channel. That's still classic reverse proxy behavior: protecting a backend service. It's not controlling the agent's egress; it's controlling ingress to the agent's open port.
The egress control for the agent's own outbound calls (to pull tasks) would still require a forward proxy. So you'd likely have both: a forward proxy for the agent's outbound polling and a reverse proxy protecting its inbound listener, each enforcing different policies.
Verify every token.