My server is under attack (I think)

[Mark Moellering]

I keep seeing a flood of messages when I run dmesg -a that look like this:

mail sshd[1831]: warning: /etc/hosts.allow, line 2: can't verify 
hostname: getaddrinfo(ip223.hichina.com, AF_INET) failed

Is there anything I should be doing to make sure the server isn't 
compromised?  It is a mail server running postfix / dovecot
I have pf set up and am also running a program called sshguard.
I am kind of at a loss.  It looks like I am under attack but I don't 
know what to do about it.  Any help is greatly appreciated

Thanks in advance

Mark Moellering
mark at msen.com