Do You Have a Wifi Intruder?

Category: Wireless

Is your Internet service sometimes mysteriously slow? It's possible that you're unwittingly sharing your wifi with a stranger. But how can you know for sure if a neighbor (or a malicious hacker) has tapped into your wifi? Read on to learn how you can detect bandwidth bandits, and give them the boot...

Is Someone "Borrowing" Your WiFi?

There are many possible reasons why your wireless Internet connection suddenly slows to a crawl. An unauthorized user stealing your bandwidth is one of them. It is unlikely that such a bandwidth thief will access your WiFi network if you have implemented the basic WiFi security described in my article, Wireless Network Security Checklist.

But it’s certainly a possibility that should be checked. Anyone with the skills and determination to hack your secured network is probably up to some sort of criminal activity. There are many casual, even “innocent” bandwidth moochers who see an available network and just assume it’s OK to “borrow” it. If they are challenged for a password when they attempt to log on, they'll probably just give up and move on to another target. If you haven't bothered to assign a wifi access password, the front door to your network is wide open.

A real cybercriminal is another matter. He is out to steal something of value from you or others. He may peruse computers on your network for identity and financial information he can use or sell. He may use your Internet connection to download files illegally or hack other networks, setting you up as the fall guy when the crime is traced back to your router. This sort of crook has the tools and skills needed to defeat most WiFi security measures, especially if you have a weak password.

Wifi Hacking

Windows and Apple computers have built-in utilities that show what devices are connected to your network. You can use these tools to look for unknown computers that should not be connecting to your network. Obviously, the first step is to know what devices are authorized. Each authorized computer should be assigned a computer name that you can recognize easily, i.e., "Jane PC" or "Billy Laptop". Other devices, such as printers, will have built-in names such as “HP Model 8610.” Other common wifi-connected devices are streaming boxes (Roku, ChromeCast, FireTV) and digital assistants such as Amazon Echo and Google Home. You should be familiar with what you own.

Detecting Unwanted Wifi Connections

In Windows 7 and 8, click the Start button and type “network” in the search box. Click on the word “Network” which should be one of the first items in the search results. On Windows 10, open Control Panel, then click "Network and Internet" then click the "view network computers and devices" link. A multi-part display of connected devices will appear, listing computers, media devices, network infrastructure, and other items connected to your local network. “Computers” will include PCs and Macs. “Media devices” include printers, gaming consoles, smart TVs, and the like. “Network infrastructure” includes your Internet router and/or modem. "Other Devices" will include streaming video players, such as a Chromecast or Roku.

For some reason, connected iPods, tablets and smartphones do not show up here. An unauthorized device will probably be among the “computers” listed, but if (for example) you see an Xbox that doesn’t belong to you, you obviously have an interloper. Apple OS X computers have a similar utility. You can access it via Finder > Go > Network. On a Linux computer, the nmap command will show connected devices.

Your router’s configuration program provides a better view of ALL devices connected to your network. By logging into your router, you can see a list of devices that currently have IP addresses assigned to them. Consult your router’s documentation (or Google it) to learn how to access this list. Devices that may appear in this list include desktop and laptop computers, tablets and ebook readers, iPods, smartphones, wireless printers, streaming devices such as Roku or AppleTV, gaming consoles, and television set-top boxes.

Many routers also store logs of past connections, which you can peruse to see what devices connected when you weren’t looking. If you don't know how to login to your router, or you don't know the password, ask your Internet Service Provider for help.

If you discover an unauthorized user on a secured WiFi network, my advice would be to immediately change BOTH your router login password and your wifi access password (see my Wireless Network Security Checklist link above) and then restart your router. If the intruder re-appears, it’s time to contact your Internet Service Provider, or maybe even call the cops.

Real-Time Wifi Monitoring

None of the utilities described so far alerts you when an unauthorized device connects to your network. A third-party utility called Softperfect Wi-Fi Guard does, though. Running in the background, it checks your router’s network connections list at intervals that you can set. Popup alerts tell you when a new or unknown device is detected. The free version of this program may not detect all your connected devices, but the paid version ($19) will.

Wireless Network Watcher is a similar free utility program that simply lists your connected devices. Optionally, it will beep when a device connects or disconnects from your router.

Another option is Advanced IP Scanner. This is a free network scanning tool that checks your network connections and displays all connected devices. It also gives you access to shared folders, provides remote control of computers, and can even remotely switch computers off.

Your thoughts on this topic are welcome! Post your comment or question below...

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Most recent comments on "Do You Have a Wifi Intruder?"

Posted by:

13 May 2019

We have an Android App, FING, on our phone that probes the network to list all attached devices.
List past and present connections.
Try it Bob, you'll lov it.

Posted by:

Bob K
13 May 2019

I have a little utility "Who is on my Wifi" that scans my LAN and alerts me if there is any new connection I haven't identified.

But, I have a weather station that uses my Wifi to connect out, and I have never been able to detect what IP address it is using, MAC address, or anything about it. When I set it up, I did have to give it my Wifi password, but that was it. If it can be invisible to me, can't others?

Posted by:

Mike Davies
13 May 2019

Avast Free Antivirus for both computers and smart phones has a built-in wifi checker. Just click to run.

Posted by:

13 May 2019

This is a standing question, not a comment, and a suggestion for a future column.

How can one tell if one's router has been compromised? We hear about different attacks on routers themselves, where they can be hacked and taken over by bad actors. How can we tell? Are there programs we can run that detect if our router is running a Denial of Service attack on some one else? Or if it is capturing our keystrokes and send them elsewhere?

Posted by:

13 May 2019

On my Win10 laptops "view network computers and devices" says network discovery is turned off. It tells how to turn it on, but when I go there it says turning it on will mean my computers can see the other devices on the network AND they are visible to others on the network. Is this part totally safe? I don't mind other users in the house seeing me, but can any hypothetical intruders also learn more about my computers?

Posted by:

13 May 2019

All routers have a functionality to identify connected users. To check this out, log in to your router’s admin panel. In Status option, the router will show all the devices connected to the WiFi. Procedure to locate Unauthorized user is similar in all the routers. Options may vary according to the router manufacturer.
Based on the Router configuration, model, and features, you can block these unidentified devices based on their Mac address. However, this is a temporary solution to prevent the intruders from your WiFi.
Once you identify the intruder on our network, the next option to block them. Do not depend on the device IP to prevent the device, since the IP address allocated to the devices are dynamic and change occasionally. Most of the device blocking protocol is using the Mac address to identify the device and block them. The user blocking can be done with your Router interface (depends on the router) or you have to buy some additional devices like Fing Network Security System or another router interface from Google WiFi.

Posted by:

13 May 2019

Thanks for providing Advanced IP Scanner link. The second I downloaded using it my entire system froze. Since I use Avast I had to contend with more of their product(s) I might (not) need going into overdrive substantiating their raison d'etre. God! It took awhile but I got system going again and have since uninstalled Advanced IP Scanner file. Sometimes I think I'm better off to take risks than protect myself 8 times over from wifi intruders.

Posted by:

Warren T
13 May 2019

Have Win 10 Home build 1809 and per your instructions "On Windows 10, open Control Panel, then click "Network and Internet"".... no such link exists to find what is connected to my network ????

Posted by:

13 May 2019

Just to let everyone to know ... Softperfect Wi-Fi Guard can be gotten for free when you download the earlier versions.

I have been using We-Fi Guard for several years now, after reading about this little program in one of Bob's previous articles. I happen to LOVE this program. It simply stays in your taskbar and takes very little resources. Plus, the program does notify me when someone signs on to my DSL Modem.

What I want to tell all of you ... You can still get a FREE version, when you download one of the older versions of Wi-Fi Guard. You will have to find a website that truly has the older versions. Do not use CNET or any of the more common websites, because they will show the older versions but you will be downloading the newer PAID version that only gives you a trial version.

This is where I got my version, when I had to re-install everything on my computer. This is where I went to get Wi-Fi Guard earlier version of Softperfect Wi-Fi Guard 1.0.7 version. It notifies you when someone comes on your Internet DSL Modem or Cable Modem. Download that program and you will see that everything in that version works just fine. Here is the URL for getting this version.

Try it, I think you may like it as much as I do. Thanks Bob for your earlier article that gave me this program, that I happen to love.

Posted by:

Allen L
13 May 2019

Same problem as Warren T (my build is still 1803 for some reason - evidently Microsoft has forgotten about me).

Posted by:

13 May 2019

Warren T: if you view your Control Panel by Category instead of Icons you will see the Network and Internet heading to click on.

Posted by:

13 May 2019

My control panel does not have a Network and Internet option.

Posted by:

13 May 2019

Warren, Allen, Kenneth: your Control Panel has three ways to view it (small delta in upper right)- Category, Large Icon, and Small Icon. If you selec the View of Category you will see the Network and Internet option.

Posted by:

14 May 2019

File Explorer also has a "Network" link

Posted by:

30 Nov 2019

Thanks brother

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