From owner-freebsd-questions@freebsd.org Mon Jul 26 13:42:56 2021 Return-Path: Delivered-To: freebsd-questions@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 388E166CCB5 for ; Mon, 26 Jul 2021 13:42:56 +0000 (UTC) (envelope-from 4250.82.1d4d2000a921678.90a34611a9beabdd739eabcca96d80dd@email-od.com) Received: from s1-b0c6.socketlabs.email-od.com (s1-b0c6.socketlabs.email-od.com [142.0.176.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4GYLhv0Fgxz4cGv for ; Mon, 26 Jul 2021 13:42:54 +0000 (UTC) (envelope-from 4250.82.1d4d2000a921678.90a34611a9beabdd739eabcca96d80dd@email-od.com) DKIM-Signature: v=1; a=rsa-sha256; d=email-od.com;i=@email-od.com;s=dkim; c=relaxed/relaxed; q=dns/txt; t=1627306975; x=1629898975; h=content-transfer-encoding:content-type:mime-version:references:in-reply-to:message-id:subject:cc:to:from:date:x-thread-info; bh=zHYwTQhRxeSDOvCfFySB8tX91Y0hiuqICL0Z9MQIbkI=; b=Ragb4cd3qoyqCV0qez3+ZBIZo3g1jxk4yZBh/8srHfLOs5p/mV5A6rpWkCHu25p74zlASO0GWCQYUFozmGSsowSDZqaYIsw5F8z5c4fNzIgJusL8lNGEdyHlXgIVRwR7/WZ8Ev36x6VNrr/m8bny9Udq5uwF08+JiWjlnMtDmx4= X-Thread-Info: NDI1MC4xMi4xZDRkMjAwMGE5MjE2NzguZnJlZWJzZC1xdWVzdGlvbnM9ZnJlZWJzZC5vcmc= Received: from r1.us-east-2.aws.in.socketlabs.com (r1.us-east-2.aws.in.socketlabs.com [142.0.189.1]) by mxsg2.email-od.com with ESMTP(version=Tls12 cipher=Aes256 bits=256); Mon, 26 Jul 2021 09:42:41 -0400 Received: from smtp.lan.sohara.org (EMTPY [185.202.17.215]) by r1.us-east-2.aws.in.socketlabs.com with ESMTP(version=Tls12 cipher=Aes256 bits=256); Mon, 26 Jul 2021 09:42:40 -0400 Received: from [192.168.63.1] (helo=steve.lan.sohara.org) by smtp.lan.sohara.org with smtp (Exim 4.94 (FreeBSD)) (envelope-from ) id 1m80sR-000CpO-Kk; Mon, 26 Jul 2021 14:42:38 +0100 Date: Mon, 26 Jul 2021 14:42:38 +0100 From: Steve O'Hara-Smith To: Norman Gray Cc: FreeBSD Questions Subject: Re: Detecting or mitigating syn-flood attacks Message-Id: <20210726144238.2245630e959724dc1df1794e@sohara.org> In-Reply-To: <57893A91-2180-441F-836F-66EAC526FBB8@nxg.name> References: <57893A91-2180-441F-836F-66EAC526FBB8@nxg.name> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; amd64-portbld-freebsd12.1) X-Clacks-Overhead: "GNU Terry Pratchett" Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4GYLhv0Fgxz4cGv X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=pass header.d=email-od.com header.s=dkim header.b=Ragb4cd3; dmarc=none; spf=pass (mx1.freebsd.org: domain of 4250.82.1d4d2000a921678.90a34611a9beabdd739eabcca96d80dd@email-od.com designates 142.0.176.198 as permitted sender) smtp.mailfrom=4250.82.1d4d2000a921678.90a34611a9beabdd739eabcca96d80dd@email-od.com X-Spamd-Result: default: False [-0.68 / 15.00]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; R_DKIM_ALLOW(-0.20)[email-od.com:s=dkim]; FROM_HAS_DN(0.00)[]; MV_CASE(0.50)[]; R_SPF_ALLOW(-0.20)[+ip4:142.0.176.0/20]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[sohara.org]; RCVD_COUNT_THREE(0.00)[4]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[email-od.com:+]; RCPT_COUNT_TWO(0.00)[2]; RCVD_IN_DNSWL_NONE(0.00)[142.0.189.1:received]; NEURAL_HAM_SHORT(-0.98)[-0.982]; FORGED_SENDER(0.30)[steve@sohara.org,4250.82.1d4d2000a921678.90a34611a9beabdd739eabcca96d80dd@email-od.com]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_LAST(0.00)[]; ASN(0.00)[asn:7381, ipnet:142.0.176.0/22, country:US]; FROM_NEQ_ENVFROM(0.00)[steve@sohara.org,4250.82.1d4d2000a921678.90a34611a9beabdd739eabcca96d80dd@email-od.com]; MAILMAN_DEST(0.00)[freebsd-questions]; DWL_DNSWL_NONE(0.00)[email-od.com:dkim] X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Jul 2021 13:42:56 -0000 On Mon, 26 Jul 2021 13:59:14 +0100 Norman Gray wrote: > > Greetings. > > Can anyone point me towards best-practice guidance on detecting and > mitigating syn-flood attacks, with a focus on FreeBSD? There's a paper on using syncache for the purpose: https://users.ece.cmu.edu/~adrian/731-sp05/readings/lemon-syn-cache.pdf I also see mentions of syncookies in related questions. -- Steve O'Hara-Smith