Date: Mon, 06 Feb 2006 11:03:39 -0600 From: Kevin Kinsey <kdk@daleco.biz> To: Brad Gilmer <bgilmer@gilmer.org> Cc: freebsd-questions@freebsd.org Subject: Re: sshd possible breakin attempt messages Message-ID: <43E7816B.7040300@daleco.biz> In-Reply-To: <20060206162304.GA83056@gilmer.org> References: <20060206162304.GA83056@gilmer.org>
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Brad Gilmer wrote:
>Hello all,
>
>I guess one of the banes of our existance as Sys Admins
>is that people are always pounding away at our systems
>trying to break in. Lately, I have been getting hit
>with several hundred of the messages below per dayin my
>security report output...
>
>gilmer.org login failures:
>Feb 5 11:18:17 gilmer sshd[78078]: reverse mapping checking getaddrinfo for 206-171-37-232.ded.pacbell.net failed - POSSIBLE BREAKIN ATTEMPT!
>Feb 5 11:18:18 gilmer sshd[78080]: reverse mapping checking getaddrinfo for 206-171-37-232.ded.pacbell.net failed - POSSIBLE BREAKIN ATTEMPT!
>Feb 5 11:18:20 gilmer sshd[78082]: reverse mapping checking getaddrinfo for 206-171-37-232.ded.pacbell.net failed - POSSIBLE BREAKIN ATTEMPT!
>
>I am running FreeBSD 5.4 RELEASE, and right now this
>box is not a production machine, but I am going to be
>taking it live fairly soon. Questions:
>
>1) Is there anything I should be doing to thwart this particular attack?
>
>
IANAE on security, but there are several possibilities. Here are a couple
ideas from my deadbeat security brain:
1. edit /etc/ssh/sshd_config and make sure that only the right users
and such are allowed to login, and via the right methods.
2. If the situation allows, you can wrap sshd via /etc/hosts.allow to
only allow logins from certain IP addresses (i.e., wherever you
intend to admin this box from).
Note that, as I mentioned, IANAE, and there is plenty of other "higher
level" security actions that can be taken to secure a box from attack.
Maybe some less-newbie-than-me guru will step up to the plate on that;
maybe not.
>2) Given that I am on 5.4, should I upgrade my sshd or do anything else
>at this point to make sure my machine is as secure as possible?
>
>
Check the advisories at the freebsd.org web site, and keep tracking
RELENG_5_4 with cvsup/buildworld, etc. to stay up to date is a good
starting point.
>3) (Meta-question) - Should I upgrade to 6.0 before I go live to be
>sure I am in the best possible security situation going forward?
>Should I wait until 6.1 for bug fixes (generally I am opposed to n.0 anything).
>
>
>
Meta-answer, if possible from an idiot like me: 6.0 is actually a very
notable exception to the "don't grab the zero release" rule in my case.
YMMV, of course. Last week I upgraded my last 5.X boxen to 6.X, and
I don't plan on looking back! Now, if I could just find time to
backup/reinstall that 4.X boxen that's locked up so far away!!!
>Thanks
>Brad
>
>
You're welcome.
Kevin Kinsey
--
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