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Little Snitch can block internet traffic of a particular app. Can I do something similar without (paying) Little Snitch?

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Little Snitch is completely worth the price. Buy it. You will thank me. –  Josh Jun 20 '13 at 18:44
@Josh Nice try, Little Snitch marketeer. ;) –  Mathias Bynens Jun 21 '13 at 6:00
@MathiasBynens haha, I am not connected with them, just a long time user and being a developer myself, someone who can appreciate a well-built piece of software –  Josh Jun 21 '13 at 11:43

5 Answers 5

up vote 11 down vote accepted


TCPBlock is a lightweight and fast application firewall ... you can prevent selected applications on your computer from opening connections to the network.

TCPBlock is currently free and can be downloaded here.

PF Firewall

OS X comes with the PF firewall, which can be configured to block all connections to certain servers in all apps. Blocking all connections from a single app is not possible as far as I am aware without external software.

You can use IceFloor as a GUI for the PF firewall.

IceFloor Black List

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Can you really block apps from IceFloor? –  dstonek Jan 21 '14 at 21:44
I'm using IceFloor v2.0.2. Can you explain your answer a bit more on how to block a specific application from accessing internet? –  Manu Sep 1 '14 at 5:01
@grgarside: in IceFloor v2.0.2 there is no Black list tab anymore.. –  ccpizza Nov 23 '14 at 14:21
tcpblock.wordpress.com is no longer available. –  J. C. Leitão Jan 22 at 23:40
macupdate.com/app/mac/35914/tcpblock new home of tcpblock? –  barrycarter Jul 6 at 13:53

TCPBlock still works in OSX Yosemite. install it, restart the machine, open system preferences and select TCPBlock. Unlock the pane then select the plus icon then Select Applications and choose Adobe Photoshop

enter image description here

(sorry about download.com link)

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Little Snitch allows setting rules per process, server, port, etc. Furthermore, you can have multiple sets of rules, e.g. I have one that I use when I want all apps to have their Internet activity disabled except browser.

Little Snitch Rules

The original question is How to block internet traffic of an application?. While you have referred to Little Snitch as not suitable (presumably due to the cost), it is a product that can block internet traffic of an application.

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I think you can through the firewall as stated in this article:

  1. Click the System Preferences icon in the Dock.
  2. Click the Security icon.
  3. Click the Firewall tab.
  4. Click the Start button to turn on your firewall.
  5. Click the Advanced button.
  6. Click the Automatically Allow Signed Software to Receive Incoming Connections radio button to select it.

This enables the firewall. And, by default, virtually all incoming TCP/IP traffic is blocked. You must enable each sharing method that you want to be able to use. When you enable different sharing methods from the Sharing pane in System Preferences (such as File Sharing or FTP Access), you’ll notice that those types of traffic now appear in the Firewall list. (In other words, when you turn on a sharing method, the firewall automatically allows traffic for that sharing method, which Snow Leopard calls a service.)

Click the up/down arrow icon to the right of any service to specify whether the firewall should allow or block connections.

Sometimes, you might want to allow other traffic through your firewall that isn’t on the firewall list of recognized services and applications. At that point, you can click the Add button (which bears a plus sign) to specify the application that your firewall should allow. Snow Leopard presents you with the familiar Add dialog, and you can choose the application that needs access.

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It seems to me Firewall only blocks incoming traffic to an app but not outgoing traffic from an app. –  ohho Jun 19 '13 at 1:08
Yes, the default firewall in OS X (as edited in this way) only blocks incoming traffic. It does not block outgoing connections from apps on your computer. The default OS X PF firewall blocks both ways (see my answer). –  grgarside Jun 20 '13 at 14:37

Use Radio Silence. Very simple application, but does the job nicely.

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Welcome to Ask Different! Radio Silence appears not to be free. Also try linking people to what you are talking about... radiosilenceapp.com –  unknowndomain Jul 17 at 20:40

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