Date: Sat, 6 Dec 2003 11:36:28 +0900 From: horio shoichi <bugsgrief@bugsgrief.net> To: freebsd-questions@freebsd.org Subject: Re: ipfilter traffic blocking and tcpdump snort etc Message-ID: <20031206.023648.5283e90dba6730f9.10.0.3.9@bugsgrief.net> In-Reply-To: <20031205105839.GC65445@users.munk.nu> References: <20031205002412.GA37507@users.munk.nu> <20031205.103353.985d01b49b9f3980.10.0.3.9@bugsgrief.net> <20031205105839.GC65445@users.munk.nu>
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On Fri, 5 Dec 2003 10:58:39 +0000 Jez Hancock <jez.hancock@munk.nu> wrote: > Hi Horio, > > Cheers for reply. > > On Fri, Dec 05, 2003 at 07:33:49PM +0900, horio shoichi wrote: > > On Fri, 5 Dec 2003 00:24:12 +0000 > > Jez Hancock <jez.hancock@munk.nu> wrote: > > > Hi, > > > > > > I've blocked a dozen or so addresses using ipfilter: > > > > > > block in quick on fxp0 from 208.186.60.116 to any > > > block in quick on fxp0 from 216.230.149.11 to any > > > > > > etc > > > > > > but I still see a lot of traffic those hosts in trafshow, snort and > > > other packet capturing utils. Why is this? > > > > You are probably seeing the supposedly blocked packets on the "outside" of > > network. Observe them on "inside", i.e., on the interface not fxp0. > Not sure what you mean here, what command would you issue via tcpdump or > snort to do what you suggest? Um, that's my bad assumption ! I thought your box is a filtering router, and has at least two interfaces. > > > What you are seeing are packets ipfilter is just about to handle. > Right - it's just I would have thought that ipfilter handled packets > before they reached any traffic dumping utils. I see what you're > getting at. Presumably snort for example uses the bpf driver via pcap(?) to > capture network traffic... > > actually reading bpf(4) clears things up a little: > > Associated with each open instance of a bpf file is a user-settable > packet filter. Whenever a packet is received by an interface, all file > descriptors listening on that interface apply their filter. Each > descriptor that accepts the packet receives its own copy. > The "log" keyword on blocking rules would have helped... > > > Is there any alternative method of blocking access from certain hosts > > > so that this traffic is not 'seen' by higher level /userland apps? > > I don't understand your second question. Are you thinking about tcp wrapper, > > reset feature of snort, etc ? > Let me rephrase that one :P I meant is there a method - for example > such as adding some kind of routing via arp - so that packets are > dropped on the floor even quicker than they would be via the firewall > method? In my observation, packet filters are the quickest since blocked packets die in ip_input(), below which is where ethernet interrupt handlers are laid out. horio shoichi > > -- > Jez Hancock > - System Administrator / PHP Developer > > http://munk.nu/ > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >
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