Do browsers need inbound/incoming firewall rules?

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Do browsers need inbound/incoming firewall rules?

Unread post by back2themoon » 2024-04-25, 11:24

I think I've asked about this in the past, but couldn't find the post.

So, I've noticed that upon installation all browsers I tried add Inbound rules to the Windows Firewall. The question is... why? Brave adds a single UDP Inbound rule (local port 5353) "to allow mDNS traffic". Firefox and Pale Moon add both TCP/UDP rules, no ports specified i.e. all ports.

After a brief search, I mostly encountered two types of answers:

a) Disable them: not required, perhaps even risky.
b) Needed for some non-standard connections/applications, related to chat/streaming/gaming etc. which perhaps Pale Moon doesn't support anyway. Firefox might even need these for telemetry-related connections.

I'm fairly certain these rules were not added by Pale Moon a few years back, but at some point this changed. After some quick tests, disabling them doesn't seem to affect anything.

Any thoughts? Are there potential security risks and what are these rules needed for, exactly? Thanks.

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Re: Do browsers need inbound/incoming firewall rules?

Unread post by Pentium4User » 2024-04-25, 11:32

mDNS is being done solely by the OS if an mDNS client is installed (Avahi on Linux, Bonjour on Windows).
I don't know why a browser should be able to receive mDNS traffic.
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Re: Do browsers need inbound/incoming firewall rules?

Unread post by Moonchild » 2024-04-25, 12:16

The only firewall rules created are those for the "private" profile, i.e. loopback connections. This would be necessary for some devtools usage and doesn't actually open it up to the outside. I haven't really looked in detail when Mozilla added this because since it's private use, there would not be a risk.
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