RE: SSH connection attempts in logs.

["Nick Vaernhoej" <nick.vaernhoej () capitalcardservices com>]

Good morning,

Thank you everyone. I am realizing that I didn't ask the right question.
I am not concerned about the connection. The log entry is from the
firewall where this isn't an allowed connection. We do not have any ssh
servers accessible from the outside.
I am curious about the connection closing on tcp/0 and I failed to say
that initiating the connection on tcp/22 was one of a number I could
have chosen. There are a lot of different port numbers being hit where
they close on tcp/0

Thanks

Nick Vaernhoej
"Quidquid latine dictum sit, altum sonatur."


-----Original Message-----
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com]
On Behalf Of jason
Sent: Sunday, September 30, 2007 8:02 PM
To: security-basics () securityfocus com
Subject: Re: SSH connection attempts in logs.

I have encountered similar issues and chances are, if you do not know
who is trying to connect to you, safer to block first and respond
later.  If a an 'admin' or a 'staff' member is idiotic enough to screw
it up more then 3 times, they need a lesson in security and whatnot.
after a good row, I sincerely doubt they will login erroneously too
often.  At that point, no harm no foul.  Honestly.  As an administrator
of an SSH running machine, if you don't recognize an IP or even the
range that it's coming from, what choice do you have but to block it?
Even if  you do recognize the range and there are multiple failures?
See previous response.

Why would you need a secure shell if you didn't care who was connecting
to your boxen?

What I typically do to circumvent the default for scanners and similar
ilk is to just change the port that ssh is on or to forward from the
firewall a specific port.  I have also seen mention of 'knock' style
programs but have not had the spare time to implement a working 'knock'
setup.  At that point what do you care (for the most part) is hitting
port 22?  This just falls under basic security steps though and I am
guessing is far from new information.

Jason Tarbet
Computer Nerd
Bangor Humane Society


ChromeSilver wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Dan Denton schrieb:
>
> > Well, I wouldn't lean toward anything that tries to connect on port
22 as
> > noise. I would verify that the src IP address isn't some legitimate
attempt
> > to connect by an application that is simply misconfigured. If it's
not
> > legit, block it. In that case it's most likely an attack, or it could
be a
> > port scanner. Just my two cents.
>
>
> > xxx.xxx.xxx.xxx = them
> > yyy.yyy.yyy.yyy = me
> >
> > c=262144 m=98 msg="Connection Opened" n=187596
> > src=xxx.xxx.xxx.xxx:32881:X1 dst=yyy.yyy.yyy.yyy:22:X1 proto=tcp/22
> > c=1024 m=537 msg="Connection Closed" n=139129
> > src=xxx.xxx.xxx.xxx:32881:X1 dst=yyy.yyy.yyy.yyy:0:X1 proto=tcp/0
>
> Yep,
>
> that's my guess too. It's some kind of port scanner very likely. Since
> it isn't probing weak accounts (like root /w empty pw), so it cant be
a
> vuln scanner. But I wouldn't suggest blocking that IP, it could be a
> dial-up conn. Better do a whois on that IP and then tell the ISP that
> you're most likely being scanned from it. Then you could, eg. contact
> that person via snailmail and let it know that there's an aware admin
> online...
>
> Grz,
> ChromeSilver
>
> - --
> "If light be the brightest light...
> Wherfore then doth it shadows cast?"
> - -R.Rohonyi
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