Date: Thu, 13 May 1999 12:18:16 +0930 (CST) From: Kris Kennaway <kkennawa@physics.adelaide.edu.au> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: danny <danny@pentalpha.com.hk>, freebsd-security@freebsd.org Subject: Re: network scan? Message-ID: <Pine.OSF.4.10.9905131211500.1222-100000@bragg> In-Reply-To: <199905130222.TAA90284@apollo.backplane.com>
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On Wed, 12 May 1999, Matthew Dillon wrote: > :May 12 18:42:24 server /kernel: ipfw: 26000 Deny TCP 202.38.248.205:4359 > :a.b.c.1:1080 in via ed0 > :... > > I get this all the time from people scanning for netbios. I > usually just ignore them. If I'm in a bad mood I send a nasty gram > to the originating network. In this case they're looking for an open SOCKS proxy (so they can use it to bounce attacks against other machines, most likely). I usually do what Matt does as well - if they're scanning really heavily then I might slap a blanket ban on their IP address(es). Don't forget though that TCP connection initiations (i.e. the initial step of the 3-way handshake) can be forged if they're designed to just bounce off your firewall (i.e. not actually connect to anything which may be listening) - so watch out for cutting off connectivity to a legitimate client. > :... > ipfw: 2010 Unreach UDP 209.156.6.31:1142 209.157.86.63:161 in via de0 > :... > ipfw: 2010 Unreach UDP 209.156.6.31:137 209.157.86.63:137 in via de0 > :... > > Windows machines like to attempt NetBIOS connections to machines on the internet when you do things like connect to a website - a lot of the UDP 137-139 traffic is harmless noise (AFAIK it always connects from port 13x to port 13x as in the above example). There's no excuse for probing SNMP ports though. Kris ---- "That suit's sharper than a page of Oscar Wilde witticisms that's been rolled up into a point, sprinkled with lemon juice and jabbed into someone's eye" "Wow, that's sharp!" - Ace Rimmer and the Cat, _Red Dwarf_ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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