HOWTO: Detect and Defeat Wifi Intruders
Is your wireless Internet connection sometimes mysteriously slow? It's possible that you're unwittingly 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...
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 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.
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 PC" or "Billy Laptop". Other devices, such as printers, will have built-in names such as “HP Model 8610.” You should be familiar with what you own.
Detecting Unwanted Wifi Connections
In Windows 7 and higher, click the Start button and type “network” in the search box. Click on the word “Network” which should be the first item in the search results. 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.
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 free third-party utility called Who's On My Wifi for Windows or Mac does, though. Running in the background, 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. Some advanced features (including blocking unwanted devices) and technical support are available with the paid "Who’s On My Wifi Online" service, but this is not required to use the free versions.
Another option is WiFi Guard. This is a network scanning tool that checks your network connections at a user-specified interval (1-60 minutes) and alerts you if it finds any new connected devices that could possibly belong to an intruder. I found it much easier to use than Who's On My Wifi. Optionally, it can play a sound, execute a command, or send an email when an event occurs. WiFi Guard is free for Windows, and $10 for Mac.
Your thoughts on this topic are welcome! Post your comment or question below...
This article was posted by Bob Rankin on 22 Dec 2015
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Article information: AskBobRankin -- HOWTO: Detect and Defeat Wifi Intruders (Posted: 22 Dec 2015)
Copyright © 2005 - Bob Rankin - All Rights Reserved