Date: Tue, 23 Jun 2009 18:59:10 +0200 From: Erik Norgaard <norgaard@locolomo.org> To: Daniel Underwood <djuatdelta@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: Best practices for securing SSH server Message-ID: <4A4109DE.3050000@locolomo.org> In-Reply-To: <b6c05a470906230653i6ce647c1p415e769b63d9e169@mail.gmail.com> References: <b6c05a470906221816l4001b92cu82270632440ee8a@mail.gmail.com> <4A406D81.3010803@locolomo.org> <b6c05a470906230653i6ce647c1p415e769b63d9e169@mail.gmail.com>
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Daniel Underwood wrote: >> I do not believe that tricks like running ssh on a >> non standard port or using port-knocking provide >> much extra security. > > I can understand that varying the port is not a very strong defensive > measure, but I don't understand your point about port-knocking. > > If you configure a complex and seemingly random sequence of knocks > before allowing an IP access to your ssh port, have you not > significantly strengthened your ssh server? A port-knocking sequence is really nothing different than a shared password. Since there is no user dialog, the sequence has to be known by all users accessing the system. Basically you ask your users to authenticate twice - don't you think you could get the same security with a standard deployment insisting on good passwords or better yet, using keys? You add an extra layer of inconvenience and complexity, more things that can fail and possibly result in an insecure server: - dynamically updating firewall rules on the interface facing the Internet is not on my list of good practices. loading or flushing rules continuously is the recipe for service interruption or exposing your server to the net. - nor is having a sniffer daemon putting the network interface in promiscuous mode, a daemon that listen on lots of ports! that really sounds attractive. (yup: that's the latest version on portknocking.org). And it can result in people being unable to access if the knocks are filtered at the source. BR, Erik -- Erik Nørgaard Ph: +34.666334818/+34.915211157 http://www.locolomo.org
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