Date: Mon, 27 Oct 2003 11:06:52 +0200 (EET) From: Jarkko Santala <jake@iki.fi> To: Kris Kennaway <kris@obsecurity.org> Cc: security@freebsd.org Subject: Re: Best way to filter "Nachi pings"? Message-ID: <20031027110203.B96390@trillian.santala.org> In-Reply-To: <20031027080240.GA9552@rot13.obsecurity.org> References: <200310270731.AAA23485@lariat.org> <20031027080240.GA9552@rot13.obsecurity.org>
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On Mon, 27 Oct 2003, Kris Kennaway wrote: > On Mon, Oct 27, 2003 at 12:31:46AM -0700, Brett Glass wrote: > > We're being ping-flooded by the Nachi worm, which probes subnets for > > systems to attack by sending 92-byte ping packets. Unfortunately, > > IPFW doesn't seem to have the ability to filter packets by length. > > Assuming that I stick with IPFW, what's the best way to stem the > > tide? > > Block all ping packets? Most security-conscious admins do this D'oh? I like ping very much and it would make me very sad indeed if I couldn't ping my boxes to solve possible network problems along the way. I fail to see the security problem and possible DoS issues could be solved by using limiting of sort. Definitely this block-all approach is not sane, its like if someone complains about NFS being broken you'd say disable it. Filtering packets by length on the other hand is a very nice feature to have. =09-jake --=20 Jarkko Santala <jake(=E4t)iki.fi> System Administrator http://iki.fi/jake= /
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