Is Someone Stealing My WiFi?

Category: Wireless

Is your wireless Internet connection sometimes mysteriously slow? It's possible that you're sharing it 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...

How to Detect and Defeat Wifi Intruders

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 serious criminal activity.

There are many casual, even “innocent” bandwidth thieves 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. If you're not sure why that's a bad idea, see The WiFi Security Mistake You Must Avoid.

Wifi Hacking

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.

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's PC" or "Billy-iPod". Other devices, such as printers, will have built-in names such as “HP Model 8600;” you should be familiar with what you own.

Detecting Unwanted Wifi Connections

In Windows 7, click the Start button and type “network” in the search box. Double-click on the word “Network” which should be the first item in the search results. A three-part display of connected devices will appear: computers, media devices, and network infrastructure. “Computers” will include PCs, smartphones, and tablets. “Media devices” include printers, gaming consoles, smart TVs, and the like. “Network infrastructure” includes your router and the modem to which it connects, typically labeled “Internet gateway device.” Note that for some reason, connected iPods 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.

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 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 nifty third-party Windows utility called WhoIsOnMyWiFi does. Running in the system tray, it checks your router’s network connections list at intervals that you can set, typically every two minutes. Audible and popup alerts tell you when an “unknown computer (is) found.” You can mark a device “known” and it won’t trigger an alert again. The program comes with a 30-day free trial. For $34.95, you get unlimited use, updates, and the ability to selectively “block” devices that try to connect to your network even if they provide the correct password.

However, it’s important to understand what this “blocking” really does. The “blocking” feature is really more of a “jamming” feature. From what I can tell, it's similar to a denial of service attack, but you become the "attacker," flooding the intruding computer's network. It does not stop an intruder from connecting to your router, but it does prevent them from accessing the Internet and any devices on your network.

My intuition tells me this would necessarily have some impact on the speed of your wireless network. Perhaps a better idea, if an intruder is detected, would be to change your router's wifi access password, then restart the router. That would boot the intruder from your network entirely, without continuously draining network resources.

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

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Posted by on 21 May 2013

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Most recent comments on "Is Someone Stealing My WiFi?"

(See all 27 comments for this article.)

Posted by:

Peter Ridgers
22 May 2013

BT broadband hubs have two wifi channels - the subscribers and a second 'public' channel (so that they can advertise thousands of free access points). Do you feel there is any security risk leaving this 'public' service active and un-monitored?

EDITOR'S NOTE: That reduces the risk of malicious intruders accessing your files. But it does nothing to prevent people from using your Internet connection to commit crimes.

Posted by:

Mark Jacobs
22 May 2013

I can go into my router settings and whitelist all the MAC addresses of any devices I want to allow to use my Wi-Fi, of I can allow all connections and blacklist any that I don't want. I like the whitelist option, which although not hard to circumvent, adds an extra layer of security if I have a strong password. Essentially, that is doing manually what WOMW does except for the continuous monitoring. Don't all routers have something like that?

Posted by:

22 May 2013

Typing "network" and clicking on the search result "network" does not reveal anything on my windows 7 machine. It's blank.

Posted by:

23 May 2013

I would suggest Disable "Broadcast of SSID",a looooong Alphanumeric special char., case sensitive password to connect, as well as encryption (WPA2-AES+)I personally put my wireless "Guest NET" in a DMZ on a FireWall. Route all DMZ traffic to WAN only. Deny all DMZ to LAN traffic.
First they have to find it, then crack my Scrabble password & encryption, only to be rewarded w/I-Net connectivity but no LAN connectivity.

Posted by:

23 May 2013

Also use MAC address filtering and change the "channel" from the default on your wireless router to anything else.

Posted by:

bob price
23 May 2013

I would like to know how to protect hotel/motel wifi connections to my laptop. Or can it be done? If you were on a public [hotel] wifi right now and ran the 'network' test, would it indicate just you or everyone in the hotel using it?

EDITOR'S NOTE: Public wifi is not secure, unless you're using an encrypted (HTTPS) connection.

Posted by:

23 May 2013

Re. In Windows 7... What if you are a MAC user?

EDITOR'S NOTE: The router method (which is best) will work for any operating system.

Posted by:

24 May 2013

It's great to understand the concepts,terminology & protocols behind the dilema of network abuse by neighbors. However, I'm just simply interested in which program I can use to control these unwanted users of my wifi. Please advise.

EDITOR'S NOTE: But I did just that in the article!

Posted by:

24 May 2013 for a FREE product similar to whoisonmywifi

Posted by:

25 May 2013

I admit I am one of those who parks my car near an available Wifi connection and uses it to surf the net. Your article was well-timed, and I intend to stop this with effect from today. Thanks.

Posted by:

26 May 2013

I use a free "Wireless Network Watcher" from on my system connected to my router.

Posted by:

27 May 2013

While I agree with all you suggest, I feel you missed a REALLY key suggestion. Most routers have a "MAC Filter" that will allow you to pre-determine which devices can connect. If a MAC address is not on the list, access is denied.

Should you not wish to use the MAC filter that way, it can generally be used to deny access to listed devices. Don't just change the password, get the MAC address that was accessing your router and deny access to it through the MAC filter!

A few believe filtering to allow devices is sufficient security; I do not. But I strongly believe it is a valuable tool and use it on all my routers.

Posted by:

What is MiFi
28 May 2013

I am impressed with the content you provided. I want to thank you for this informative article. I enjoyed each aspect of it and I will be waiting for the new updates For Mi-Fi.

Posted by:

28 May 2013

If you want to check if your neighbor is connected to your wifi, you have a very simple program to use. Wireless Network Watcher

You can download it from:

Posted by:

30 May 2013

I downloaded the trial version yesterday. Today I left for about 45 minutes, came back and YUP... WhoIsOnMyWifi caught one on my wifi. I shut down and unplugged the router.. gave it 15 minutes and rebooted. Nothing since.

I do have a couple of Net Watcher programs from Nirsoft and NEITHER of them caught this.

Blocking doesn't work on Windows 8. Wondering how long it will be before they come out with a version that Blocking Will work with W/8.

Posted by:

30 May 2013

Agree with Ric's posting of 24 May 2013.
A nifty little tool that stands quietly by and picks up an intruder instantly. My Son was connecting all of his electronics, and every time he plugged something else in, the alert popped up immediately. You can set it to scan automatically from a minute up to an hour. It can also scan up to 32 devices. I enjoyed the article Mr. Rankin. Thank you.

Posted by:

30 May 2013

my router keeps a list of all devices connected to it - or once connected to it - unless it is reset or rebooted. In other words, if you periodicly check your router by typing in your routers address into your browser and checking the device table. IF a stranger is there, or was there, his MAC address is listed so just go to the MAC filter and deny access to that computer.

Posted by:

04 Jun 2013

I live in New York City and see vendors selling decoder which can crack open password protected wifi in seconds. Is there any method more secure than password?

Posted by:

09 Jun 2013

I also agree with Ric's posting of 24 May 2013.
Just installed it and seems to work really great!
Thanks to you Bob,also,as I just got wifi and didnt know the dangers.

Posted by:

11 Dec 2013

This article is frivolous. Learned nothing. "Protection" mentioned here is ridiculous, but I'm not going to give You details coz it could leave me without free inet.
Actually Im going to give You one advice: use Kali Linux. It has live DVD so you dont have to install it.

EDITOR'S NOTE: Sorry you didn't learn. Hopefully with all your accumulated knowledge, you can become gainfully employed, and then you can afford to pay for an Internet connection, so others less fortunate can mooch off yours. How much does high-speed Internet cost in Serbia?

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