the ping command

open new command prompt as root user and execute commands
#ps -ef | grep ping | grep -v grep
this command will bring you a list of ping processes
first number is the process number which you have to kill by this command
#kill -9

Don't put angle brackets put only the process number

First to do, go to the console where you made the ping command and then press Ctrl-c. This will stop the process. If it doesn't stop the ping command then go to another console and type

ps -ax|grep ping

identify what PID (process ID) has the ping command you made. Process ID's are in numbers, then type

kill -9

Check if the process is still running by issuing the ps -ax|grep ping again. If all the options i mentioned are not working then you might have no other choice thanto reboot. good luck!.