Date: Tue, 15 Jun 2004 23:29:46 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: Robert Downes <nullentropy@lineone.net> Cc: freebsd-questions@freebsd.org Subject: Re: Firewall rules Message-ID: <20040615202946.GB1116@gothmog.gr> In-Reply-To: <40CF53FA.7070308@lineone.net> References: <40CF53FA.7070308@lineone.net>
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On 2004-06-15 20:54, Robert Downes <nullentropy@lineone.net> wrote: > I'm obviously missing something... > > su-2.05b# ipfw -a list > 00100 16 1144 divert 8668 ip from any to any in via rl0 > 00200 17 964 divert 8668 ip from any to any out via rl0 > 00300 0 0 check-state > 00400 32 3296 allow ip from me to me > 00500 21 1268 allow ip from 192.168.0.0/24 to any keep-state > 00600 274 25875 allow ip from 192.168.1.0/24 to any keep-state > 00700 2 96 deny log ip from any to any > 65535 4 429 deny ip from any to any > > Now, having seen plenty of examples of huge lists of rules, I'm > obviously not seeing something that is apparent to others. Perhaps. This depends on what you mean to achieve. > I've tested my network using the grc.com ShieldsUp! port probing > system. It informs me that every one of the first 1056 ports is > stealthed (i.e. does not even reply to probes). That's because the canonical behavior of a host that doesn't listen on a TCP port is to return RST replies when connection attempts are seen. You'd need something like this added to your ruleset: add 301 deny tcp from any to any established add 601 reset tcp from any to any > In fact, the only thing it complains about is the fact that my IP > replies to ICPM ping requests (though I don't understand how). I think rule 65535 should catch these, but I haven't used ipfw in a very long time and I might be mistaken. Anyway, if you are limiting ICMP replies through the net.inet.icmp.icmplim sysctl pings shouldn't be a source of trouble. > And my /var/log/security file shows that dozens of random connections > to ports 135 and 445 have been dropped. So, what am I missing? You're missing a lot of Windows viruses. Ports 135 and 445 are used by Microsoft-specific protocols (Location Service and Directory Services, respectively). What you're seeing is a lot of attempts by trojans and other viral programs trying to break into your "Windows" machine. - Giorgos
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