Tightening up ssh

fbsd_user fbsd_user at a1poweruser.com
Sun Mar 26 20:54:08 UTC 2006

The fact of life is there is no way to stop ssh logon attacks
as long as you have port 22 open to the public internet.

You all ready see ssh doing its job correctly by not
allowing unauthorized logons.

Review the questions archives, this subject has been beat
to death the last 3 weeks.

There are some port application that read the hosts.allow log and
auto creates firewall rules to block that attacking ip address.
But this is just busy work as it does not stop the packets
hitting your front door or really add any additional security
over what native ssh is providing you.

A more popular method is to change the port number ssh uses and
just have your remote ssh users use that port number when they
remote logon to ssh.

Now the mass majority of script kiddies & robots attackers will
find port 22 closed and lose interest in you.
Only an dedicated attacker who has it out for just you, and knows
your ip address all ready would make the special effort to scan all
the high order port numbers looking for a ssh response.

Read the end of this doc for more details on how to change ssh's
port number.

Direct link to "Example of Host SSH & Win SSH Clients" is

-----Original Message-----
From: owner-freebsd-questions at freebsd.org
[mailto:owner-freebsd-questions at freebsd.org]On Behalf Of Graham
Sent: Sunday, March 26, 2006 2:52 PM
To: mark at mkproductions.org; questions freebsd
Subject: Tightening up ssh

Hi Mark:
You recently wrote:

"Users are encouraged to create single-purpose users with ssh keys
and very narrowly defined sudo privileges instead of using root
for automated tasks."

Does this mean that there is a way to run ssh, but only allow
certain users to use it.   My default seems to have been that if
someone has a username and password they can access ssh (except root
as "PermitRootLogin no" is the default).   The ssh port seems to be
the most heavily attacked one on my machine and so I recently took
to blocking port 22.   My preference would be to enable it to only
one user and give them an obscure username and strong password.
Root is not currently allowed access by default in the setup.

Is this the approach that you alluded to above?   Can you point me
to some information or provide some tips.
Thanks,  Graham/


Kindness can be infectious - try it.

Graham North
Vancouver, BC

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