Q&A: Whose Are These Unknown Devices Connected to My Network?

Q: How can I tell if an unauthorized person is on my wireless network?

A: You find strange files on your desktop, messages written to yourself in your email, and your available connection drops from 20 megabits a second to 1.5.

I kid.

In all sincerity, there’s a good reason to check and see to just how many devices your router has currently assigned IP addresses. You get a refresh of just how many people and devices you’ve authorized to use your protected network at any given time. More importantly, it gives you some peace of mind to see that nobody has managed to break in your network’s back door when you weren’t looking.

Discovering systems connected to a D-Link router is super easy. Access your router’s Web-based configuration screen by typing the router’s IP address (D-Link routers typically use 192.168.0.1) into the address bar of a Web browser, and then log in to the gateway. Look for a navigation element on the left sidebar that’s called “Network Settings,” or some derivative of the phrase depending on your exact router model, and click that.

Scroll to the bottom of the “Network Settings” page, and you’ll see a small table representing the systems to which your router has dynamically assigned an IP address. A few of these entries might give you some kind of description in the “Hostname” field, like “Android” for a smartphone or the actual name you or a guest has assigned his or her system. And a few of these might simply say, “UNKNOWN.”

To find out the exact identity of these devices, as well as their owners, you could write down the listed MAC addresses and ask all your guests to hand over their wireless devices for a comparison — an effective but party-pooping technique. Other than that, you don’t have much recourse for matching the exact identity of a MAC address with a person. But you can at least tell how “open” you’ve let your network become.

This example also illustrates why you should always assign your own systems legitimate hostnames whenever possible, which will help you more easily identify your own systems on your network (and separate verified devices from interlopers). In Windows, this is as easy as going to Control Panel and clicking on the System icon. Depending on your version of the OS, you might have to first click on the “Change Settings” option under the “Computer Name” section. Regardless, you’ll soon reach the System Properties window. Click on the “Computer Name” tab and click the ”Change” button to edit your system’s hostname to a more descriptive title — like “DiningRoomPC” or “MagicalFloatingLaptop,” for example.

Now that you’ve identified the party crashers on your network, you need to give them the boot and ensure they can’t get back in. That requires a wireless security protocol — but which one? I’ll cover that in my next post.

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