With all those articles around on hackers, NSA, the Chinese spying, etc. one gets worried. I sit on my MAC island, so a more secure environment. But a few days ago I got the creeps, noticing very heavy traffic on my router. Checked the network activity, finding some useless programs doing stuff on the Internet (Canon scanner stuff). Thanks to Google search I managed to kill that one. Still, in one day some 1 GB of data came into my MAC. Never got the explanation: it was apparently not related to any software update. Well at least it was not outgoing: like someone copying my hard disk. Tried all different gimmicks to identify the culprit(s). Activity Monitor allows to see the traffic but not which program is doing it. One way is to kill one by one suspicious-looking activities in Activity Monitor (get info and then force quit). Another way is to use nettop command using terminal:
http://reviews.cnet.com/8301-13727_7-57580828-263/use-nettop-command-to-check-per-application-network-activity-in-os-x/
I must admit, the results are not so clear unless you are a specialist.
I did check my firewall and shut down any access that I was not using (sharing printers etc.).
Still, my router continued to flicker madly while Activity Monitor showed little if any incoming or outgoing traffic. After two days, it stopped.
I can only guess some hacker was furiously trying to hack my laptop. No clear way to see who is “knocking on my door”… But I always keep an eye on my router light…
Or?