From owner-freebsd-security Wed Sep 16 23:44:27 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id XAA02044 for freebsd-security-outgoing; Wed, 16 Sep 1998 23:44:27 -0700 (PDT) (envelope-from owner-freebsd-security@FreeBSD.ORG) Received: from shell6.ba.best.com (shell6.ba.best.com [206.184.139.137]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id XAA02012 for ; Wed, 16 Sep 1998 23:44:22 -0700 (PDT) (envelope-from jkb@best.com) Received: from localhost (jkb@localhost) by shell6.ba.best.com (8.9.0/8.9.0/best.sh) with SMTP id XAA06109; Wed, 16 Sep 1998 23:43:57 -0700 (PDT) X-Authentication-Warning: shell6.ba.best.com: jkb owned process doing -bs Date: Wed, 16 Sep 1998 23:43:55 -0700 (PDT) From: "Jan B. Koum " X-Sender: jkb@shell6.ba.best.com To: john cc: freebsd-security@FreeBSD.ORG Subject: Re: Are we vulnerable to "stealth" port scans? In-Reply-To: <199809170319.WAA18072@leonardo.cascss.unt.edu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org I wouldn't use the word "vulnerable", but yes, most TCP stacks will in one way or another respond to Steal scans. On my system I modifed kernel to log via net.inet.tcp.log_in_vain sysctl variable not only SYN packets but all other packets. If someone would be to do this stealth scan on you, you could still notice: Sep 11 22:58:50 twentythree /kernel: Connection attempt to TCP 199.51.61.23:1 from 199.51.61.22:1<6>FIN<6>RST<6>PUSH<6>URG<6> Sep 11 22:58:50 twentythree /kernel: Connection attempt to TCP 199.51.61.23:1 from 199.51.61.22:1<6>RST<6> Sep 11 22:58:50 twentythree /kernel: Connection attempt to TCP 199.51.61.23:1 from 199.51.61.22:1<6>ACK<6>FIN<6>RST<6>URG<6> Also, one can setup something like NFR to watch for port scans on the network. -- Yan I don't have the password .... + Jan Koum But the path is chainlinked .. | Spelled Jan, pronounced Yan. There. So if you've got the time .... | Web: http://www.best.com/~jkb Set the tone to sync ......... + OS: http://www.FreeBSD.org On Wed, 16 Sep 1998, john wrote: >See http://www.2600.com/phrack/p49-15.html >for a description of two "stealth" port >scan methods. > >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