Dig: The dig (Domain Information Groper) command is similar to the nslookup command, but is easier to use from the UNIX command line.
The command gathers information from the DNS based on the detected IP address, and obtains the corresponding host name and any other information that is available about the computer which caused the alarm to occur. This option is equivalent to entering the following UNIX command:

/usr/bin/dig -x ipaddress any any