Date: Mon, 14 Jan 2002 16:26:52 +0100 From: Krzysztof Zaraska <kzaraska@student.uci.agh.edu.pl> To: "Haikal Saadh" <wyldephyre2@yahoo.com> Cc: freebsd-security@freebsd.org Subject: Re: Which intrusion detection to use? Message-ID: <20020114162652.7ba2a6d4.kzaraska@student.uci.agh.edu.pl> In-Reply-To: <004c01c19d0a$4e0cf3b0$6dc801ca@warhawk> References: <20020113210809.6be9f991.kzaraska@student.uci.agh.edu.pl> <004c01c19d0a$4e0cf3b0$6dc801ca@warhawk>
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On Mon, 14 Jan 2002 19:46:38 +0500 "Haikal Saadh" <wyldephyre2@yahoo.com> wrote: > *snip* > > > I don't know how tight your particular setup is, but if you > > deny access to all unused ports to the world there will be no > > use in PortSentry since the offending packets will never his > > the port PortSentry is listening on. Snort does not care > > about firewalls, so just tell it to listen on outside > > interface and you're set. > > > > I have been thinking about this a bit lately. I am (was until I broke it > this morning upgrading to 1.8.3, blast it!) running snort and ipfw, and > while I would get ipfw dropping packets in my logs, I have nothing in my > snort alerts from my outside network. (Quite a few from the inside > though, mostly malformed NetBIOS packets and other mostly harmless (as > far as I'm concerned) traffic). > > My firewall policy is default deny, but with dynamic rules so that I can > actually use stuff. My snort's HOMENET is set to any, and I'm on dialup. > > > What I'd like to someone to clarify for me is: > Is snort actually seeing incoming packets on my outside interface, and > I've been really lucky so far > OR > Is snort not hearing anything on my outside interface? (tun0) From my experience snort will not catch much in this setup. If you deny anything you are virtually invisible for kiddiez out there. They usually sweep large networks looking for alive hosts and then look closer at those who are alive. But if you deny everything you are a dead host for them. These sweep scans are not detected by snort, since it does not trigger on single SYN or PING packet. And you do not have any services running, so no exploits are tried on you. Snort is libpcap based, so if tcpdump -i tun0 works for you snort should see packets also... There is a simple test: just portscan your box from the remote computer. This should trigger alert. [...] Krzysztof To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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