Firewall / active filter question

[Jason Crowe]

It is called stateful packet filtering. Iptables has this function 
built-in. :)

Jason

Jared Smith wrote:

>I don't know much about firewalls, so forgive me 
>if I'm suggesting something that already exists or 
>is not technically possible.
>
>As I understand firewalls, they block all ports 
>except those specifically opened, and they forward 
>IPs to internal addresses, therefore masking 
>what's happening on the inside of the network.
>
>This is passive. What I lay awake last night 
>thinking was, what about filtering in an active 
>manner? With an active filter, the only packets 
>acceptible are those which have been specifically 
>requested. You'd have a buffer which kept track of 
>all outgoing requests, and waited for a few minutes 
>to receive them. Everything else would be rejected.
>
>Seems like this would make it impossible for people
>to hack in, unless they were actively monitoring 
>outgoing packets. While this wouldn't work for a 
>server (which needs to accept arbitrary hits), it 
>would work for a surfer.
>
>Does this already exist?
>
>-Jared
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