this may cause another debate -
Mac OS firewall is off by default. I do not run any service that needs incoming traffic to my server. I have turned all remote access to NAS, etc. Any downside of turning the firewall on?
I previously bought Little Snitch and installed on my previous Mac but did not bother to re-install on my current Mac, should I ?
None that Iâve experienced. Other than the likelihood you may need to tweak its settings occasionally to get 3rd party software to work properly. OTOH unless youâve got some sketchy IOT devices, etc. on your network Iâm not sure how much it will add to your security.
I used to run Little Snitch but havenât in recent years. As I recall I wasnât able to identify all the outbound connections an iMac made after a fresh install of OSX with Little Snitch being the only software installed. Tracking hundreds of connections can be a real time suck. On the plus side trying to identify all those connections will make you an expert Google user in short order.
IMO, for most users it can be a constant source of anxiety.
Lately you can do that by saying âI like toast & jamâ 
Personally, Little Snitch is the first thing I install on any new Mac. My brain is set to littleSnitch.installPriorityLevel = 'WinRAR'
IMHO if you have a router with a firewall thereâs really no reason to turn on the macOS firewall.
At home, youâre probably OK, but I would always recommend Security in layers so I would switch it on.
If itâs a mac you travel with and add to random Wi-Fi then you should turn it on.
thatâs a good point, security level should be different for cable connected and Mac at home versus those used traveling and connected to public wifi , etc
this is another good point, IOT manufacturers can be from all over the place and hard to know what backend communications they are sending as âbonusesâ
further thought, IOTs traffic could be directly through the router and not via Mac, so even little snitch would not know?
This is an excellent point, which I overlooked because I donât have a laptop. If youâre using, say, hotel wifi, you should definitely turn on macOSâ firewall.
Jam is for slow-witted people and you should be chastised for even suggesting otherwise.
They could also attack other local devices, so switching on your Mac firewall should protect it.
You need to butter before spreading the jam on first 