you can always use task manager and just blow most any program away
however an AV usually loads deep into your os
so you might not get as much resources back as you think you should
better to reboot and keep it from loading
then NO INTERNET ACCESS unless you are running VM or Sandbox or equivalents
The cure is worse than the disease
what exactly is your problem?
what os, firewall, other programs
how fast a system- how much memory etc