Curious case of denyhost and ssh.

I been using denyhost on my own server and many other boxes i been taking care of.

I was getting error whenever i tried connecting to my server
“ssh_exchange_identification: Connection closed by remote host”

After checking logfile i figured that its happening because of the denyhost. The documentation at the denyhost website explains how to remove the blacklisted Ip

Now i had to find real issue why is my legitimate IP getting blacklisted again and again?

My logfile gave me a Warning

Aug 25 16:39:34 vm27 sshd[13147]: reverse mapping checking getaddrinfo for [] failed – POSSIBLE BREAK-IN ATTEMPT!

To get this error removed what i did was, I had to add UseDns no to /etc/ssh/ssd_config file.

This removed warning messages and also i was not getting anymore issue of getting IP blocked from denyhost.