Date: Sun, 7 Mar 2010 15:41:14 -0500 From: dacoder <dc@dcoder.net> To: freebsd-questions@freebsd.org Subject: Re: Thousands of ssh probes Message-ID: <20100307204114.GK16274@mail2.dcoder.net> In-Reply-To: <4B91B36D.1020507@locolomo.org> References: <20100305125446.GA14774@elwood.starfire.mn.org> <4B91B36D.1020507@locolomo.org>
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+++ Erik Norgaard [06/03/10 02:44 +0100]: >On 05/03/10 13:54, John wrote: >>My nightly security logs have thousands upon thousands of ssh probes >>in them. One day, over 6500. This is enough that I can actually >>"feel" it in my network performance. Other than changing ssh to >>a non-standard port - is there a way to deal with these? Every >>day, they originate from several different IP addresses, so I can't >>just put in a static firewall rule. Is there a way to get ssh >>to quit responding to a port or a way to generate a dynamic pf >>rule in cases like this? > >This is a frequent question on the list, search the archives. Basically >there are few things that you can do: > >1. limit the access to a range of IPs, for example, even if you travel a >lot you go to al limited number of countries, why permit access from >other continents? > >2. limit access to certain users, there is no need to allow games or >root user to authenticate via ssh. Use AllowUsers or AllowGroups to >restrict access to real users. > >3. limit the amount of concurrent non-authenticated connections, number >of failed attempts and similar. > >4. prohibit password authentication. > >If the problem is that these attacks consume significant bandwidth then >moving your service to a different port may be a good solution, but if >your concern is security, then the above is more effective. > >BR, Erik > >-- >Erik Nørgaard >Ph: +34.666334818/+34.915211157 http://www.locolomo.org >_______________________________________________ >freebsd-questions@freebsd.org mailing list >http://lists.freebsd.org/mailman/listinfo/freebsd-questions >To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" -- has anybody suggested having sshd listen on a high port? regards, david coder network engineer emeritus, verio/ntt telluride, co & washington, dc
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