Many of my Mac-owning friends don’t know that OS X comes with a built-in firewall, a simple network security system that can control incoming and outgoing network traffic to and from your Mac. You might wonder what good a firewall can do to enhance your Mac’s security because Apple doesn’t even both to turn it on. That’s right, the firewall’s default setting is off. Crazy, right?
Computer firewalls can be complicated devices and Apple builds in additional layers of security so even with the firewall turned off the OS X remains a tough nut to crack. But like they say, a little paranoia is good once you find out that hackers and thieves are out to get you and are doing all they can to break into your Mac.
Here’s a simple and free way to use OS X’s built-in firewall to add another layer of security to your Mac. It’s a free firewall utility called Murus Lite, a simple front end user interface for OS X’s software firewall. It’s not a firewall app itself; merely a front end to the built-in firewall on a Mac.
To turn on the Mac’s firewall, open System Preferences, click Security & Privacy, then click the Firewall tab. Options are nominal and you’ll need to authenticate to turn on the firewall and change settings. Firewalls can be complicated beasts with a long list of arcane settings which Murus aims to make easier and mostly point and click.
Nearly everything you need to improve security and lock down your Mac just a bit tighter than out-of-the-box settings is available in Murus Lite (with more options in the full version). As an example, Murus gives you controls over bandwidth throttling, a runtime PF rules browser, and a bunch of useful presets that are little more than drag and drop or point and click.
Firewall rules to prevent access (or allow access from the network) can be set by dragging and dropping appropriate icons in the interface and selecting the right checkboxes. That opens or closes specific numeric ports within the firewall which allows or prevents remote access. You won’t need to know code or even understand firewall rules syntax. And all OS X firewall default settings can be retained with a click.
That makes Murus Lite a relatively safe way to learn how to use a firewall while giving your Mac another layer of security from the outside world that Apple chooses not to make easily available to Mac users. Note, thought, that Murus Lite only runs on OS X Yosemite (it uses a mixture of Swift, Objective-C, and C++ to create the code) but firewall configurations can be copied from a Mac running OS X Yosemite to a Mac running, say, OS X Mavericks (it’s also a cumbersome, manual process not for the faint of heart).