Date: Sat, 12 Jun 1999 00:46:33 +0300 From: Ruslan Ermilov <ru@ucb.crimea.ua> To: Pete Fritchman <petef@netreach.net> Cc: "Jason L. Schwab" <jschwab@royal.net>, ghandi@mindless.com, freebsd-security@FreeBSD.ORG Subject: Re: firewalls Message-ID: <19990612004633.A29090@relay.ucb.crimea.ua> In-Reply-To: <Pine.LNX.3.96.990611171436.3504B-100000@static-petef.netreach.net>; from Pete Fritchman on Fri, Jun 11, 1999 at 05:15:07PM -0400 References: <Pine.BSF.4.10.9906111420020.92798-100000@fkr.dynip.com> <Pine.LNX.3.96.990611171436.3504B-100000@static-petef.netreach.net>
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On Fri, Jun 11, 1999 at 05:15:07PM -0400, Pete Fritchman wrote: > You probably just want to deny all icmp to your dialup. > > ipfw add deny icmp from any to any > > -------------------- > [ Pete Fritchman ] > [ Systems Engineer ] > [petef@netreach.net] > -------------------- > Don't do it!!! It will broke Path MTU discovery: http://www.worldgate.com/~marcs/mtu/ Instead, use ICMP_BANDLIM option: * Add ICMP_BANDLIM option and 'net.inet.icmp.icmplim' sysctl. If option * is specified in kernel config, icmplim defaults to 100 pps. Setting it * to 0 will disable the feature. This feature limits ICMP error responses * for packets sent to bad tcp or udp ports, which does a lot to help the * machine handle network D.O.S. attacks. * * The kernel will report packet rates that exceed the limit at a rate of * one kernel printf per second. There is one issue in regards to the * 'tail end' of an attack... the kernel will not output the last report * until some unrelated and valid icmp error packet is return at some * point after the attack is over. This is a minor reporting issue only. Cheers, -- 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-security" in the body of the message
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