How to Open Ports with Portmaster Network Monitor

Jack Wallen demonstrates how to open a port in Portmaster to allow secure shell traffic to a desktop computer.

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Portmaster isn’t just a cross-platform network monitor – it’s also a very powerful security tool that can help lock down your desktops and block things like ads, trackers, and malware. I use Portmaster on my main Linux desktop and can attest to its ability to block incoming traffic.

I recently had an incident when for some reason (probably because I was feeling lazy and didn’t want to make the trip to my office at the end of the house) I had to SSH into on my desktop from another machine on the LAN. I had forgotten that Portmaster was working and I hadn’t yet established a rule to allow that particular IP address. No matter what I tried, I couldn’t get in. But after adding the allow rule, entry through the required port was allowed and everything was fine.

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I would like to show you how to add such a rule to Portmaster so that you too can allow specific traffic into a machine.

What you will need

For this to work you will need to install Portmaster. It doesn’t matter which operating system you use, because Portmaster’s user interface is the same across the board. However, I will demonstrate opening the SSH service to an IP address. If your machine doesn’t include SSH, you’ll need to trade that service for something else.

How to open Secure Shell port

Open the Portmaster interface, which can be done from your system tray if it’s already running. In the main window (Figure A), click the Application Overview button.

Figure A

The Apps Overview icon is in the blue square.

In the resulting window (Figure B), type sshd in the search field.

Figure B

The Portmaster applications overview window.

Click on the sshd entry and in the new screen scroll down until you see the Incoming Rules section (Figure C).

Figure C

The Incoming Rules section of the sshd entry.

The first thing you want to do is make sure Block Connections is ON, because you don’t want any SSH connection to be allowed. Then click Add Rule.

In the Select drop-down list, select Allow, then enter the IP address you want to allow through the SSH port (Figure D). When you’re done, click the check mark to save the rule.

Figure D

Allow to pass through the firewall.

One thing I’ve noticed is that it’s always best to add the inbound rule before trying to SSH into the machine. I’ve had cases where after attempting an SSH connection, adding the rule for that IP didn’t work. However, I’ve never had an instance where Portmaster’s global rules would block a connection if the rule was added before an SSH connection attempt. The lesson here is to always add rules before trying to connect.

And that’s all there is to opening a port with Portmaster. I have found this application to be an invaluable tool not only for locking down my desktops, but also for much better and easier control over what is allowed in and out of a given system. I highly recommend this free, open-source tool for all your desktops and laptops – and, if they have a GUI, your servers too.

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