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Month: August 2016

Re: [trinity-users] fail2ban advice needed

From: Gene Heskett <gheskett@...>
Date: Sat, 27 Aug 2016 14:29:23 -0400
On Saturday 27 August 2016 14:08:58 Steven D'Aprano wrote:

> On Sat, Aug 27, 2016 at 10:46:31AM -0400, Gene Heskett wrote:
> > Greetings all;
> >
> > Is there someone familiar with fail2ban here?
> I'm not an expert, but I do run it myself.
> > I just installed it and started it with the installation defaults,
> > which I do not know since the init script has no "dump" option.
> Look at the default config file:
> less /etc/fail2ban/fail2ban.conf
> and the jail file:
> less /etc/fail2ban/jail.conf
> > However that bit of hungry guard dog only protects this machine,
> > leaving the other 4 or sometimes 5 on my local network still open.
> >
> > So specifically, is there a way to broadcast the rules it applies to
> > the other 4 or 5 machines, protecting them at the same time?
> The way I would do that would be to install fail2ban on each machine,
> and then periodically rsync the relevant config files from one
> designated "master" copy to the other machines. You can probably set
> that up as a cron job.
> Actually, that's not really how I would do it. How I really would do
> it would be to ensure that only one machine is directly exposed to the
> internet. Let's say I had four machines, "groucho", "harpo", "chico"
> and "zeppo". Plus, of course, my modem/router has a firewall. So I
> would have:
> (ASCII art best viewed in a fixed-width font, like Courier)
>                  internet
>                  firewall (router/modem)
>                  groucho
>             +-------+-------+------------+
>           harpo           chico        zeppo
In my lashup, although groucho has two ethernet ports, groucho is on an 8 
port switch in parallel with harpo, chico, and zeppo.  The switches 
upstream port goes to the router. So all machines have instant access to 
the net with the router keeping track of who originated the net traffic 
request. ssh -Y using keyfile access control is transparent from this 
machine to the others.  As is an sshfs mount to /home/me on all the 
other machines.  Root access by ssh is denied.  Where there is more than 
one machine in a building/room, an additional hub tee's things off.
> groucho, of course, also runs its own firewall, giving defence in
> depth: even if router firewall is compromised, the firewall on groucho
> gives some additional security. harpo, chico and zeppo don't have any
> firewall because they're all part of my trusted LAN. (You may not
> trust your LAN, in which case by all means put firewalls on
> everything.) Nothing can go directly from the internet to the inner
> LAN, so groucho is the only machine that needs to run fail2ban.
> To SSH into chico, say, I would SSH into groucho, then SSH into chico.
> There's probably a clever way of doing that in a single step with ssh
> tunnelling, but that's beyond my level of expertise, so I just do it
> with two steps.
> > Or possibly broadcast them to the router, which is running dd-wrt,
> > and which is considered one of the more bulletproof reflash's about.
> > I may be lucky, but since I do have a port forward to allow my web
> > server, there is a potential attack point.
> Does your router have a writable storage area? Apart from its own
> configuration, of course?

Yes, one can add to its rules, but access is a cast iron b---h.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
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