MacOS – multi-home High Sierra and block one address

macosNetwork

I run Apache on my Macbook Pro for off-line use of a web app. But for "self-defense" online, I use /etc/hosts to map certain hostnames to 127.0.0.1 which means if a webpage causes a GET to one of these, it hits my local webserver instead.

I would rather they do nothing. If I point them to an address that I know is unreachable, e.g., 10.250.250.250, then a poorly designed web page may not render until the GET times out.

In 10.13.4, how do I (Can I) point them to a separate private address that will be handled on the Macbook and set that address to immediately reject everything? (Without changing how loopback behaves.)

(By the way, Apple documentation has long claimed that /etc/hosts is only used in single-user mode. I have found that to be false on many versions of OS X/MacOS.)

Best Answer

The easiest way to achieve a guaranteed reject with no timeout is to use a broadcast address 255.255.255.255. Edit your /etc/hosts file and for hosts that you want request rejected put an entry such as:

255.255.255.255  rejectedhost.com
255.255.255.255  someotherhost.net

This free and simple technique can also be used to block out advertisement hosts on ad-ridden or popup-ridden web pages.

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MacOS – Sharing one IP address among multiple Apple devices

Yes, but with caveats.

MacOS X has an "internet sharing" mode in the "Sharing" control panel, but you have to use different network interfaces for the "internet facing" and "internal facing" sides of your network.

So if you're connected to the Internet over your ethernet port, you can share your connection to WiFi clients. What you can't do is connect and share over the same port.

IMac – Block all sites except one

Check out Parental Control. This allows to restrict applications to run as well as web sites to visit.

Alternatively you can use ipfw to restrict IP/Internet access:

 sudo ipfw -f flush
 sudo ipfw add allow tcp from me to xx.xx.xx.xx
 sudo ipfw add allow ip from me to xx.xx.xx.xx
 sudo ipfw add deny tcp from me to any
 sudo ipfw add deny ip from me to any

To disable just run sudo ipfw flush again

Best Answer

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MacOS – Sharing one IP address among multiple Apple devices

IMac – Block all sites except one

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