From owner-freebsd-ipfw@FreeBSD.ORG Wed Sep 25 17:36:15 2013 Return-Path: Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id DDF0294F for ; Wed, 25 Sep 2013 17:36:14 +0000 (UTC) (envelope-from netops.admin@epsb.ca) Received: from mail-ob0-f194.google.com (mail-ob0-f194.google.com [209.85.214.194]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id A91CB25D3 for ; Wed, 25 Sep 2013 17:36:14 +0000 (UTC) Received: by mail-ob0-f194.google.com with SMTP id gq1so1697705obb.1 for ; Wed, 25 Sep 2013 10:36:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:date:message-id:subject:from :to:content-type; bh=nOu9zaQld1aiIDV7k/WgIxfirdnlgqg0T3ZmqI22zdk=; b=NapDVCsKyTTGrtCJuJtc6c9A55bgA25yghxx+Fj0x7/JNFC/P0XQ4okXZUFuKi1Is9 rWY4RumDsXJ+65OPjuqjUsQ/O0lF8tggOzEh44oAi+mc6AntNAGFV+CpCEaXfW4Y68P1 D+TOXZCsHiJ4BcN0WQ77O1fyqVUYTat/yScQ8yAp7vWapKh0QaFwFLmznq9VlVtGw3jL M3n98I00TMqeeU5vv2iOot0qJcoRLD/T38sMRFIrdYh+fZjxMy9XIbGO2pxFSsXlK3DF 8DX7SRN2Ekf8RiJxAbuUoEsJxt99FifDduC7xYa657Nd3t4uyDRweCO2WxmFAgf6770K v9lg== X-Gm-Message-State: ALoCoQlYwPBb6H4sB/Fqhcg1q2cZ0HNx/JfPEss+5nzT6mh7a2wJlEzBFztjNjIns1D3iFl5a+X79MUytaBZ/AhMmAwUTdUZBuGgS0/JIe5jHJC5jQ8Y5qqq0V6qQ16V0mQqjuCaF90E MIME-Version: 1.0 X-Received: by 10.60.60.71 with SMTP id f7mr1287841oer.82.1380129801292; Wed, 25 Sep 2013 10:23:21 -0700 (PDT) Sender: kirk.davis@epsb.ca X-Google-Sender-Delegation: kirk.davis@epsb.ca Received: by 10.60.26.2 with HTTP; Wed, 25 Sep 2013 10:23:21 -0700 (PDT) Date: Wed, 25 Sep 2013 11:23:21 -0600 X-Google-Sender-Auth: TakFFisSisLavmNMYcuWuQYz2kc Message-ID: Subject: stopping an attack (fraggle like) From: NetOps Admin To: freebsd-ipfw@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.14 X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Sep 2013 17:36:15 -0000 Hi, We are currently getting hit with a DoS attack that looks very similar to a Fraggle attack. We are seeing a large amount of UDP traffic coming at us from thousands of hosts. The source UDP port is 19 (chargen) and when it hits it consumes a 2Gb/s link. Our main router is a FreeBSD server with ipfw installed. I have tried blocking UDP port 19 incoming from the internet in a firewall rule but the UDP packets are very large and they are followed by a number of fragmented packets. I think that even though I am blocking port 19, the fragmented packets are getting though and eating up the bandwidth. I am a little hesitant of using a UDP deny rule with "keep-state" to try and block the following fragmented packets. I don't want to cause memory issues. Can I use keep-state with a deny rules? Will it have issues if I use keep-state to track thousands of hosts in a saturated 2 Gb/s link? Any ideas on how others are controlling this? Thanks ----- Kirk