Firewall / active filter question

[Dustin Decker]

On Fri, 13 Dec 2002, Jared Smith wrote:

> 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.

This is called "stateful packet inspection" in most cases.  Just about 
every decent firewall out there (and hopefully all the home grown 
ipchains/iptables scripts as well) do this.

Dustin
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