try turning off any "real-time" software that runs constantly.. namely antvirus software and the like. i don't know equivalent for mac - but turning off some 'useless' services can help too.
if you have ever run any "optimizing" software, undo those changes and uninstall that software. they don't work. it's just a gimmick 99.999%, anyway.
you have a firewall and your router should provide some protection, a constantly running AV software is just a security blanket that is almost guaranteed to cause more problems than any benefits it provides... if you randomly download and run random programs or install random crap from a shady website for it to supposedly "function" you may want to keep it running, or change that behaviour
