OSEC

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Re: machine hangs on occasion - correlated with ssh break-in attempts

From: Brooks Davis (brooksfreebsd.org)
Date: Thu Aug 21 2008 - 15:37:03 CDT


On Thu, Aug 21, 2008 at 10:10:42PM +0200, Rink Springer wrote:
> On Thu, Aug 21, 2008 at 01:03:09PM -0700, Jeremy Chadwick wrote:
> > Finally, consider moving to pf instead, if you really feel ipfw is
> > what's causing your machine to crash. You might be pleasantly surprised
> > by the syntax, and overall administrative usability (it is significantly
> > superior to ipfw, IMHO).
>
> In fact, pf can already do this out-of-the-box, by doing something like:
>
> table <sshlusers> persist
> pass quick on $wan_if proto tcp from any to any port ssh flags S/SA keep
> state \
> (max-src-conn 15, max-src-conn-rate 5/3, overload <sshlusers> flush
> global)
>
> If that is not an option, I have found that security/denyhosts works
> pretty well too (it just adds IP's to /etc/hosts.deniedssh, and
> host_access(5) denies them based on this)

You almost certainly don't want to rate limit ssh connections, only failed
ones. If you rate limit connections and use svn, you're likely to lock your
self out.

-- Brooks

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