Port scan detection in ipfw2

Chuck Swiger cswiger at mac.com
Thu Jun 10 19:59:39 GMT 2004

Khoi Dinh wrote:
> This is a repost and I was hoping there might be a solution to this.  I was
> wondering if ipfw2 has the ability to detect port scan like iptables with
> the psd module.  I'm looking for a kernel-based solution, not app-based like
> portsentry.

ipfw performs packet inspection and it can certainly recognize the traffic 
associated with a port scan, yes.  The kernel provides support for limiting 
the generation of ICMP error messages, which is what happens when someone port 
scans a bunch of closed ports.  What else did you want to do?

> Also, is ipfw2 able to allow/disallow traffic according to
> time? ie. If I wanted to allow http traffic only from 9am to 1pm, can I do
> this with ipfw?

IPFW and IPFW2 have no notion of time, but one could very easily use cron to 
change your firewall rulesets at specific times in order to accomplish what 
you've asked for.


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