Is there a reason port knocking is not an option?

http://www.linuxjournal.com/article/6811

and

http://en.wikipedia.org/wiki/Port_knocking

I was a bit skeptical at first, but after implementing
it, /var/log/secure stays pretty silent. :-)

~kurth

On Wed, 2008-07-09 at 12:55 -0400, Zembower, Kevin wrote:
> This might seem like a strange question to ask, but is there a way to
> deliberately create a slow response to an SSH request? I'm annoyed at
> the large number of distributed SSH brute-force attacks on a server I
> administer, trying to guess the password for 'root' and other accounts.
> I think that my server is pretty secure; doesn't allow root to log in
> through SSH, only a restricted number of accounts are allowed SSH
> access, with I think pretty good passwords. But still, the attempts
> annoy me.
>
> I wouldn't mind if SSH took say 30 seconds to ask me for my password.
> This would slow the attempts. Is there any way to configure OpenSSH to
> do this? I searched the archives of this group with 'slow' and 'delay'
> but didn't come up with anything on this topic. Please point it out to
> me if I overlooked anything. In addition, I can limit the number of SSH
> connections to 3-5 and still operate okay.
>
> Ultimately, I need this solution for hosts running OpenSSH_3.9p1 under
> RHEL ES 4 and OpenSSH_4.3p2 under Debian 'etch' 4.0 and Fedora Core 6.
>
> Thanks in advance for your advice and suggestions.
>
> -Kevin
>
> Kevin Zembower
> Internet Services Group manager
> Center for Communication Programs
> Bloomberg School of Public Health
> Johns Hopkins University
> 111 Market Place, Suite 310
> Baltimore, Maryland 21202
> 410-659-6139
>