Best practices for securing SSH server

Wojciech Puchar wojtek at wojtek.tensor.gdynia.pl
Tue Jun 23 06:46:52 UTC 2009


> If for some reason you would prefer to use password authentication, I
> would recommend that you look into automatic brute force detection.
> There are a number of utilities in ports available for this purpose,
> including security/sshguard and security/denyhosts.

good, but not really important with properly chosen password.
You can't do more than maybe 10 attempts/second this way, while cracking 
10 character password consisting of just small letters and digits needs

36^10=3656158440062976 possible passwords, and over 11 milion years to 
check all possibilities, so say 100000 years if someone is really lucky 
and will get it after checking 1% possible password.

Of course - you must not look at logs in 100000 years and not see this 10 
attempts per second.



I give this example against common paranoia that exist on that group - mix 
of real "security paranoid" persons and pseudo-experts that like to repeat 
"intelligent" phrases to show up themselves.

Actually - there is no need for extra protection for ssh, but for humans.

99% of crack attempts are done by "kevin mitnick" methods, not password 
cracking.


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