I’ve spent some time searching this question, but I have yet to find a satisfying answer. The majority of answers that I have seen state something along the lines of the following:
- “It’s just good security practice.”
- “You need it if you are running a server.”
- “You need it if you don’t trust the other devices on the network.”
- “You need it if you are not behind a NAT.”
- “You need it if you don’t trust the software running on your computer.”
The only answer that makes any sense to me is #5. #1 leaves a lot to be desired, as it advocates for doing something without thinking about why you’re doing it – it is essentially a non-answer. #2 is strange – why does it matter? If one is hosting a webserver on port 80, for example, they are going to poke a hole in their router’s NAT at port 80 to open that server’s port to the public. What difference does it make to then have another firewall that needs to be port forwarded? #3 is a strange one – what sort of malicious behaviour could even be done to a device with no firewall? If you have no applications listening on any port, then there’s nothing to access. #4 feels like an extension of #3 – only, in this case, it is most likely a larger group that the device is exposed to. #5 is the only one that makes some sense; if you install a program that you do not trust (you don’t know how it works), you don’t want it to be able to readily communicate with the outside world unless you explicitly grant it permission to do so. Such an unknown program could be the door to get into your device, or a spy on your device’s actions.
If anything, a firewall only seems to provide extra precautions against mistakes made by the user, rather than actively preventing bad actors from getting in. People seem to treat it as if it’s acting like the front door to a house, but this analogy doesn’t make much sense to me – without a house (a service listening on a port), what good is a door?
Sure. I’m not exactly sure any more what I was trying to convey. I think I was going for the firewall as a means if perimeter security. Usually devices are just configured to allow access to devices from the same Local Access Network. This is the case for lots of consumer electronics (and some enterprises also rely on securing the perimeter, once you get in their internal network, you can exploit that.) My printer lets everyone print and scan, no password setup required while installing the drivers. The wifi smart plugs I use to turn on and off the mood light in the livingroom also per default accept everyone in the WiFi. And lots of security cameras also have no password on them or people don’t change the default since they’re the only ones able to connect to the home WiFi. This works, since usually there is a Wifi router that connects to the internet and also does NAT, which I’d argue is the same concept as a firewall that discards incoming connections. And while wifi protocols have/had vulnerabilities, it’s fairly uncommon that people go wardriving or close to your house to crack the wifi password. However, since you mentioned mixing devices you trust and devices you don’t trust… That can have bad consequences in a network setup like this. You either do it properly, or you need some other means to secure your stuff. That may be isolating the cheap chinese consumer electronic with god knows which bugs and spying tech from the rest of the network. And/or shielding the devices you can’t set up a password on.
I don’t think you can make an absolute statement in this case. It depends on the scenario, as it always does with security. If you have broken web software with known and unpatched vulnerabilities, a Web Application Firewall might filter out malicious requests. An Application Firewall if other software is susceptible to attacks or might become the attacker itself (I’m not entirely sure what they do.) But you might also be able to use a conventional firewall (or a VPN) to restrict access to that software to trusted users only. For example drop all packets if it’s not you interacting with that piece of software. And you can also combine several measures.
Are you referring to the firewall on the router?
Interesting. I hadn’t heard of this.
As in blocking or restricting their communication with the rest of the lan in the router’s firewall, for example? Or, perhaps, putting them behind their own dedicated firewall (this is probably superfluous to the firewall in the router though).
For clarity’s sake, would you be able to provide an example of how this could be implemented? It’s not immediately clear to me exactly what you are referring to when combining “user” with network related topics.