I leave mine on in my MBP because I leave the house with it and never experienced any conflicts but on an iMac that is stationary IMO it really is user preference it probably can not hurt.
Again agree, my MBP stays @ home behind our AirPort Extreme Router, but I would certainly use the OS firewall if on the road; and using both seems to have worked out fine for others, so becomes a personal decision.
But if you plan to 'test' the firewall (alone or in combination), then be careful on how the testing is done; e.g. I visited
Steve Gibson's website which I used constantly when on PCs - his
Shields Up!! will scan a variety of ports etc. on your router or computer to determine if these are 'open', 'closed', or 'stealth' (the link provides an explanation of each).
Well, I scanned my system w/ just the router's firewall in place, all of the 1056 ports tested were closed w/ a handful in stealth mode - the closed ports had responded but of course did not permit TCP packets to pass; I then turned on my computer's firewall and checked off the 'stealth' option producing the same results (see two attached pics); of course, both times only the router was being examined - I would have to directly attach my laptop to the cable modem and then retest, i.e. the laptop would need the IP address (top of each pic) assigned to my cable modem and the router.
Now is having all ports closed enough to ask from one's router or is complete stealth the goal? I've not really delved into the more advanced settings of my fairly new router w/ the AirPort Utility - but would be curious of others' opinions regarding the level of protection desired from their routers. Dave
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