Date: Mon, 15 Mar 1999 19:41:48 +0200 From: Ruslan Ermilov <ru@ucb.crimea.ua> To: The Tech-Admin Dude <geniusj@phoenix.unacom.com> Cc: questions@FreeBSD.ORG Subject: Re: SYN attacks Message-ID: <19990315194148.A841@relay.ucb.crimea.ua> In-Reply-To: <Pine.BSF.4.10.9903151227140.29462-100000@phoenix.unacom.com>; from The Tech-Admin Dude on Mon, Mar 15, 1999 at 12:28:48PM -0500 References: <19990315100709.D64525@relay.ucb.crimea.ua> <Pine.BSF.4.10.9903151227140.29462-100000@phoenix.unacom.com>
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On Mon, Mar 15, 1999 at 12:28:48PM -0500, The Tech-Admin Dude wrote: > > > On Mon, 15 Mar 1999, Ruslan Ermilov wrote: > > > On Sun, Mar 14, 1999 at 09:51:30PM -0000, geniusj@phoenix.unacom.com wrote: > > > Hi, if this is directed towards the wrong list, please forward it to the > > > correct one.. My concern is that our server has been getting some massive > > > SYN floods from, what we think arespoofed hosts recently. It has brought our > > > system to its knees, even with its power (Dual 400 512 mb of ram). We would > > > like to somehow restrict these zombie connections from building up so much > > > .. I found somewhat of an old kernel patch, but due to the age of it, it isnt > > > applicable any more. I would like any suggestions on stopping or weakening > > > these attacks either by kernel patch or ip filtering.. Any suggestions are > > > welcome. > > > > > > Thanks, > > > Jason DiCioccio <geniusj@unacom.com> > > > > man 4 dummynet > > > <SNIP> > > That looks to be (and as I understood it) for limitting bandwidth > going through a certain device, I dont want to llimit overall bandwidth of > the system, the SYN attacks dont actually take much bandwidth, but they do > take a big chunk of system resources and dont allow anyone else to login > while they are going on.. No, you can limit only packets with SYN bit set. For example, ipfw pipe 1 config bw 1Kbit/s ipfw add pipe 1 tcp from any to <your_host> setup via <external_interface> -- Ruslan Ermilov Sysadmin and DBA of the ru@ucb.crimea.ua United Commercial Bank +380.652.247.647 Simferopol, Ukraine http://www.FreeBSD.org The Power To Serve http://www.oracle.com Enabling The Information Age To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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