How do I tell if someone is using my wireless network?

Posted By : Ken Colburn of Data Doctors on June 28, 2007 5:20 PM

Question

Is there a way to tell if someone is using my wireless network without my knowledge?

-Carey

Answer

This question was answered on June 28, 2007. Much of the information contained herein may have changed since posting.

The popularity of wireless networks in homes and businesses is due, in large part, to the ease in setting them up. Most folks can pull a wireless router of the box, plug it in and get some kind of connection in a relatively short period of time, but this also presents a problem.

The default setup for most wireless networking base stations bypass any form of security (I suspect that this helps cut down the number of support calls the manufacturer takes from new users).

Your question really needs to be answered for two scenarios; wireless networks with no security enabled and wireless networks with security measures in place.

If your wireless network is unsecured, anyone within several hundred feet of your wireless router can easily connect and use any resources that are unsecured. Depending upon the operating system your computers are running and how they have been setup, not only can a bypassing person use your Internet connection, they may have access to various files on your computers.

Invoking any level of “encryption” on your base station will require anyone that wants to connect to have the “key”, which is generated during the setup. This step will not completely eliminate the possibility of being “hacked” by someone that really wants to get to you, but it will certainly cause those looking for an open connection to move on to your unsecured neighbors.

Most every wireless router has the ability to track what machines are connecting to it and stores this information in log files.

If you are somewhat familiar with the administrative interface for your router, you can check to see what IP addresses and/or MAC addresses have been logged as users of your network (or consult your owner’s manual.)

You would then need to compare that information with the actual IP addresses and MAC addresses of the computers that you own.

The IP (Internet Protocol) address is a series of numbers that are assigned to each computer on the network, so if you only have two computers and you see that four IP addresses are currently in use, two outsiders are connected to your network.

The MAC (Media Access Control) address is a unique serial number burned into the network card of each computer that is designed to identify it from all others. If MAC addresses other than those from your computers show up on the log, you would also know that outsiders are connecting.

To find your IP and MAC addresses in Windows Vista, XP or 2000 (do a Google search for directions on other operating systems), click on the Start button then on the Run option, type “cmd” and hit the Enter button.

This will launch a window with a black background and white text (known as the Command Prompt). Type “ipconfig /all” and hit Enter and a whole host of technical gibberish will appear.

Look for the Wireless Network Connection section and then look for the line that starts with “Physical Address” (followed by 12 characters separated by 5 dash marks.) This is your MAC address and the IP address is generally a few lines below that.

If you have secured your router and think that outsiders are still accessing your network, your best bet is to bring in someone very technical to evaluate all of the signs of tampering and to setup measures to make it extremely difficult for outsiders to connect.

My recommendations for taking reasonable steps to secure a wireless network include:

- Turn off the SSID broadcast, so your router becomes invisible to the outside world

- Turn on either WEP (Wired Equivalent Privacy) or WPA (Wifi Protected Access which is considered more secure) so anyone that wants to connect must have a “key”

- Change the default username and password for the administrator account on your router so remote hackers can’t take control of it via the Internet

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Posted by Ken Colburn of Data Doctors on June 28, 2007

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