sshd possible breakin attempt messages
kdk at daleco.biz
Mon Feb 6 09:05:00 PST 2006
Brad Gilmer wrote:
>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: reverse mapping checking getaddrinfo for 206-171-37-232.ded.pacbell.net failed - POSSIBLE BREAKIN ATTEMPT!
>Feb 5 11:18:18 gilmer sshd: reverse mapping checking getaddrinfo for 206-171-37-232.ded.pacbell.net failed - POSSIBLE BREAKIN ATTEMPT!
>Feb 5 11:18:20 gilmer sshd: 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;
>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
>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!!!
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