stop PING ??

will using the ping command to the server cause any effects to the server.

i want to stop people from pinging to my server. how do i do this ??

when i query a host name trmsrv.geotrac.com in NSLOOKUP utility i get the response as ip address 4.18.8.25 , but when i PING to the same server using ping trmsrv.geotrac.com i get request timed out. how is this done ??