Ubuntu has a command that lists all current processes.If you find the process ID,you can kill it by kill command.
Type following to list all your own running processes
And use command to kill any process you want,the second column is PIDnumber.
kill -9 PIDnumber
Ubuntu also has a graphical program to view current processes.Navigate to System–>Administrator–>System Monitor,you will see system processes at Process tab,kill any by select it and click “End Process” button.