A vew days back,my macbook air got hacked.
Im behind a router with firewall.
I have all the updates for the mac os.
Mac firewall on.
I have avast anti virus for mac running.
Somehow,i got a new trojan and i found out i was hacked because my mouse cursor was moving on its own over my screen
I installed also bitdefender av and intego virusbarrier.
Non of the anti virus programs found it.

So i installed Private Eye to see whats connecting to the internet.
http://radiosilenceapp.com/private-eye

Found some things i didnt trust after googling for it and deleted them.
Because i was so angry and a bit in panic,i didnt think about sending them to the av companies
Now everything is fine according the network monitor.

But it also teached me to never trust on anti virus alone.....A network monitor installed on a mac is a big must.