[CentOS] sshd: Authentication Failures: 137 Time(s)

[Ljubomir Ljubojevic]

rrichard at blythe.org wrote:
> Indeed! I run
> Fail2Ban not only against SSH, but against SMTP/AUTH and IMAPS/POP3S (the
> only client mail protocols we support). It's amazing how many dictionary
> attacks take place against SMTP by persistent spamers! Besides the effect
> against dictionary attacks, it makes the morning reading of the secure log
> a pleasant experience. :-)

My SMTP server has Reverse DNS check active, so any SMTP request from IP 
  that does not have Reverse DNS record is automatically forbidden. Even 
SMTP servers tht are not properly configured  (like one Bank server in 
my country that sends mails from some obscure IP without DNS record even 
thou I know they are legit) are denied.

fail2ban had some wrong with it, from the standpoint of my CentOS 5.x 
server (can't remember what I disliked), wheather it was rpm 
availability or something else, so I chose denyhosts. There was whole 
week recently without a single ssh attack on my 3 PC's (2 servers).

Ljubomir