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Something is blocking on incoming connections on my Mac and I can't figure out what it is. Firewall is turned off, anti virus is turned off.

As a simple test, I'm executing:

shai@Macbook Downloads $ nc -l 12345

I can't access it from my iPhone (using the same WiFi hotspot), but when using a browser locally, I see output on netcat - which means connection succeeded.

What is going on?

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As you answered your own question, I suggest you flag this post and ask some kind moderator to undo your bounty, so you can use your reputation in future posts. – harrymc Jan 27 '14 at 14:19
We typically don't do this, but given that the bounty was only started yesterday, consider this a freebie. – slhck Jan 28 '14 at 8:54
up vote 0 down vote accepted

I decided to go over all of the log files I could find under /var/logs.

At some point, I ended up in a log file that contains DENY/ALLOW output for incoming connections. I then used lsof to figure out who's writing to that file and found the reason for this whole mess: Checkpoint Endpoint security, a VPN client that has a built-in security policy thing.

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