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This question has been asked before, but in hypothetical terms, and it received hypothetical answers: connecting a secure computer directly to the internet without a router

I recently bricked my router doing a firmware upgrade (ironically, because I recently learned of a security vulnerability in my router model that the upgrade would fix). I ordered a new one online, but it will take several days to arrive. I would like to actually use my Internet at home until it gets here.

I have exactly two uses for wired internet:

  1. Watching Netflix and YouTube videos
  2. Pulling data from my company's MySQL server

I have two distinct concerns about these uses.

The first is that, by plugging my machine directly into the Internet, I am exposing it directly to any attacks that might arrive at my IP address. I am aware that OSX has not one but two firewalls that come with it. How can I configure these correctly so that bad things don't happen while I'm watching The Bridge on the River Kwai?

The second is that I don't believe my company's database server is as secure as it could be. What steps, if any, can I take on the client side to protect our data? Or am I equally at risk in this case regardless of whether or not I am behind a hardware firewall?

I followed the suggestion in the question I linked to run netstat -an, and noticed a large number of entries like

tcp4 0  0  *.88  *.*  LISTEN

Does this mean that my computer is listening on port 88? How do I know which ports are necessary to connect to and browse the Internet, and how should I secure them?

Edit: Running without -n leads me to believe that my computer is listening for Kerberos authentication. I unchecked all of the "sharing" options, which removed the Kerberos and SSH entries, but several of these "Active Internet Connections" remain

  • Some apps may be listening, but if you have the firewall enabled they should still not be able to receive any connections so you are safe. – André Borie Aug 28 '16 at 16:50
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If you're not running any service in your workstation (which you're not) then you can simply block (drop) all incoming connections.

Usually simply enabling the firewall is enough since the default is to drop all incoming.

The rest will depend on your context, but usually you don't need outgoing filters on a workstation, so that's a lot less to worry about.

Incoming drop. Outgoing allow. Adjust as needs arise.

  • That's pretty straightforward then. The OS X application firewall has an option to block "all incoming connections except for basic Internet services" which I've enabled. – shadowtalker Aug 28 '16 at 18:42

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