If your apache server is slow and you believe it might be subject of a DoS attack, netstat is a good tool to check if this is true.

The following command will list all ipadresses with connections to your server and show how many connections are active at this point.

netstat -nap|grep \:80 | grep ESTA | awk '{print $5 }' | cut -d':' -f1 | sort | uniq -c