Put /tmp partition as a seperate partition and mount it as noexec, nosuid. Make sure that your programs php/httpd uses the /tmp for the temporary files, cache and session info. This simple steps stop 80% of attack on the server.
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Obviously he is talking about ddos attack. Im still trying to figure out how reply #2 is relavent. But anyway, using csf and ddos deflate together is not a good idea. Only use CSF with connection tracking set to a reasonable level. Adjust your web server to optimal settings - there are tons of guides and configuration suggestions on the net for this.
Personally I think as far as dealing with ddos on the server level there is no better option then litespeed web server, CSF with connection tracking, optimal tcp stack settings and various other scripts made to work with CSF, look around.
Then it comes down to how big your pipe is, how much bandwidth you are getting through it and how much resources you have on your server.