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My (application) firewall settings are configured to block incoming connections from netbiosd. I don't recall setting this myself, and wonder what the consequences are.

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What are the consequences of blocking incoming connections for netbiosd? If I generally block incoming connections as a precaution, should I block netbiosd as well?

  • Same here, but also dozens of OUTGOING connection attempts, that are even more suspicious. I am at home, with NAT and all, and I only opened one IP for outside access, and I get zillions of IPs from all around the world trying to connect to my iMac. my Firewall (same as OPs) warns, and I usually block these. But I've seen dozens of outgoing attempts, again to many IP numbers I do not know. Now WHO is trying to connect from my Mac outside using netbios, and how can I ever know which of these is legitimate? – Motti Shneor Jun 25 '16 at 13:02
  • @MottiShneor This is where a preogram Little Snitch helps it asks for each outbound connection to be allowed or denies per app and external endpoint – Mark Oct 26 '16 at 11:41
  • @Mark: Yes, that's how I first noticed the traffic, but its typically unclear just how to use Little Snitch in any given situation. Here, for example, the question still applies. – orome Oct 26 '16 at 13:07
  • I was responding to the comment and not your question – Mark Oct 26 '16 at 15:24
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netbiosd is responsible for interacting with NetBIOS networks. NetBIOS is Microsoft's networking service.

If you block incoming netbiosd connections then you will not be able to share drives over netbios which is the simplest way to share data to Windows machines.

If you generally block incoming connections as a precaution the you should block anything until you actually need it, that is until something breaks. So yes block netbiosd to begin with.

  • So is it safe to say that if I have no Windows machines there will be no consequences? Also: I don't recall ever setting this; could it somehow have happened automatically? – orome Feb 11 '13 at 16:54
  • Will I still be able to use arbitrary networks (e.g., wifi in a client's conference room; hotel wifi) if I block netbiosd incoming connections? – orome Feb 12 '13 at 15:16
  • How are you using the networks netbiosd will affect Windows file sharing and possible windows authentication but not web use etc. – Mark Feb 12 '13 at 15:18
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    → raxacoricofallapatorius: you most probably blocked netbiosd access the first time you entered a Windows network where you were immediatly bombed by all Windows neighbor netbios broadcasting like a flock of geese. MacOS X asked you if you wanted to accept or block this unsollicited access. I bet that you blocked it. And this was an excellent reflex ☺! – dan May 10 '13 at 8:16
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    A related answer also supports blocking or disabling netbiosd. – orome Feb 11 '14 at 12:53

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