From owner-freebsd-security Fri Sep 28 16:39:11 2001 Delivered-To: freebsd-security@freebsd.org Received: from mail.webmonster.de (datasink.webmonster.de [194.162.162.209]) by hub.freebsd.org (Postfix) with SMTP id DF6B437B408 for ; Fri, 28 Sep 2001 16:39:03 -0700 (PDT) Received: (qmail 37925 invoked by uid 1000); 28 Sep 2001 23:39:25 -0000 Date: Sat, 29 Sep 2001 01:39:25 +0200 From: "Karsten W. Rohrbach" To: Mike Tancsa Cc: Ronan Lucio , freebsd-security@FreeBSD.ORG Subject: Re: flood attacks Message-ID: <20010929013925.C37579@mail.webmonster.de> Mail-Followup-To: "Karsten W. Rohrbach" , Mike Tancsa , Ronan Lucio , freebsd-security@FreeBSD.ORG References: <037601c14773$52a23da0$2aa8a8c0@melim.com.br> <5.1.0.14.0.20010927125302.048abb10@marble.sentex.ca> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-md5; protocol="application/pgp-signature"; boundary="wxDdMuZNg1r63Hyj" Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <5.1.0.14.0.20010927125302.048abb10@marble.sentex.ca>; from mike@sentex.net on Thu, Sep 27, 2001 at 12:57:48PM -0400 X-Arbitrary-Number-Of-The-Day: 42 X-URL: http://www.webmonster.de/ X-Disclaimer: My opinions do not necessarily represent those of my employer X-Work-URL: http://www.ngenn.net/ X-Work-Address: nGENn GmbH, Schloss Kransberg, D-61250 Usingen-Kransberg, Germany X-Work-Phone: +49-6081-682-304 Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org --wxDdMuZNg1r63Hyj Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable just as a sidenote: some people from the net.community, prelude nids projects and me are currently thinking about implementing a real network intrusion management system which means that in the future we hopefully will be able to do active countermeasure stuff concerning dos/ddos and other network attacks.=20 there is no single line of code written yet, it's brainstorm and discussion time at the moment. if you want to join the discussion check the archive of the list [http://defender.webmonster.de/lists.html] and subscribe ;-) cheers, /k Mike Tancsa(mike@sentex.net)@2001.09.27 12:57:48 +0000: >=20 > The problem is that once its in your network, its too late so to speak. Y= ou=20 > want to involve your ISP to get them to limit it before it traverses your= =20 > link. If you are lucky the packets are not random junk and you can block= =20 > on the source IP. Are they hitting the same port ? are they coming from= =20 > random IPs ? As someone said, > sysctl -w net.inet.tcp.log_in_vain=3D1 > sysctl -w net.inet.ud.log_in_vain=3D1 >=20 > If they are not hitting random ports and hitting say your web server, > ipfw add 10 count log tcp from any to me 80;sleep 10;ipfw delete 10 > and look at /var/log/security and see where the junk is coming from. >=20 > ---Mike >=20 > At 01:41 PM 9/27/01 -0300, Ronan Lucio wrote: > >Hi Dave, > > > >But, in my case, I looked at mrtg graphics and saw that > >it had big flow during 1 hour. > >So, I supposed to prevent such situation. > > > >[ ]=B4s > > > >Ronan Lucio > > > > > > Limiting closed port RST response from 1800 to 200 packets per > >second. > > > > > > Awhile back, I managed to reproduce this by portscanning myself with a > > > very fast scanner which doesn't wait for any kind of response from the > > > server before testing the next port. The 1800 to 200 message thing s= ounds > > > quite general, so you could be getting flooded with lots of different > > > kinds of data. If the messages come in briefly and then stop for awh= ile > > > (rather than a continus flow) you could just be getting a fast port s= can. > > > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > > with "unsubscribe freebsd-security" in the body of the message > > > > > > > > > > > >To Unsubscribe: send mail to majordomo@FreeBSD.org > >with "unsubscribe freebsd-security" in the body of the message >=20 >=20 > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-security" in the body of the message --=20 > Nuclear war can ruin your whole compile. --Karl Lehenbauer KR433/KR11-RIPE -- WebMonster Community Founder -- nGENn GmbH Senior Techie http://www.webmonster.de/ -- ftp://ftp.webmonster.de/ -- http://www.ngenn.n= et/ karsten&rohrbach.de -- alpha&ngenn.net -- alpha&scene.org -- catch@spam.de GnuPG 0x2964BF46 2001-03-15 42F9 9FFF 50D4 2F38 DBEE DF22 3340 4F4E 2964 B= F46 Please do not remove my address from To: and Cc: fields in mailing lists. 1= 0x --wxDdMuZNg1r63Hyj Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: For info see http://www.gnupg.org iD8DBQE7tQotM0BPTilkv0YRAgY8AJ0b41pdhJxY7LdGn6eNIkZOM/0pTACgl3VX ShrRcYWZYU34mVVZ0HcxoP0= =N/3P -----END PGP SIGNATURE----- --wxDdMuZNg1r63Hyj-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message