Wireless Networking Security Basics

Is your wireless network safe?

 Are wireless networks less secure? What can I do to make my wireless network more secure? We’ll take a look at some tips you can use to decrease the likelihood of having someone hack your wireless network inside this article.

First off, let’s start off with the hard truth. Wireless networks are by nature insecure, at least compared to wire based networks. That’s just a fact of nature. Does this mean we shouldn’t use them? Not at all. It does however mean that we should take some basic precautions when using them. In this article we will be looking at some basic things that you can do to help tighten down the security of a home or small business wireless network.

Technology changes rapidly, so things could change at any time, which make it easier to hack wireless networks, such as new exploits for the protocol being discovered. At the same time, there are a lot of people researching ways to make wireless security more secure. Keep this in mind while reading this article and during the future.

 

This article will be broken down in a “tips” kind of format. I will list items that you can do, give a description of that item, then move on to the next “tip”. At the end of the article, I will recap with a list of steps that have been covered as a brief overview. I am in no way implying that the tips in this article are the end all of wireless security, but they do help tighten things down. Also, I am covering this in a generic way. I am not going to focus on any one vendor, i.e. I am not talking about specifically Apple AirPort, Linksys, NetGear, D-Link, Cisco or any individual vendor. The tips covered herein should apply to any access point that implements wireless standards.

 

How do people even find wireless networks?

There are a lot of pre-canned tools that can be used to find wireless networks and determine a fair amount of information about them. Almost every operating system has at least one tool, most have several, just dedicated to wireless network identification and probing. Since this article is for Mac users, we will take a quick look at one of the tools for OS X. The tool I am talking about is called Mac Stumbler. This little application will allow you to determine if there is a wireless network within range, what it’s SSID is, the actual signal strength, the channel it is running on, the vendor of the access point and whether or not the access point is using WEP encryption. All of this just from launching a little application. It is a no brainer to walk or drive around with this app running on your laptop and see what access points are available and quite a few that you find are wide open as well. Not a good thing for the owner.

Now that we have seen how easy it is to find open access points, what do we do to keep others from finding our access points and using them as easily? We’ll cover the basics here. A quick list is: Encrypt, Filter, Signal Control and Kill Broadcasts. Let’s look at these things in more detail now.

Encryption:

Use the WEP encryption that is built into pretty much all access points. I know that this security is minimal. It can be cracked. However, it will discourage the casual hacker and the script kiddie that doesn’t have the right tools and skills to crack the network. This will in turn cause them to go and look for an easier target to break into, leaving your network in its pristine shape. Unfortunately, since someone can break this encryption with the right knowledge and skills, we will want to take additional steps to secure our wireless networks. So, let’s continue.

 

Filtering:

What is filtering? Filtering is the process of not allowing any computer to connect who has not been added to an allow list. How is it done? You log in to your access point and look for the filtering option. It is usually listed in an “Advanced” area. Insert all the MAC addresses that you want to allow to connect. What is a MAC address and how do I find it. A MAC address is a unique hardware id that is burned into all network interface cards (NICs). Where can I find the MAC address on my computers? In OS X, it’s easy. Open your System Preferences, go to the Network Pane, make sure that Airport is selected, and you will see at the bottom an Airport ID that looks similar to this: 00:23:91:ed:14:2b. That is your MAC address. Other Operating Systems have other means of determining them. With a Windows box, you tend to run winipcfg or ipconfig /all and choosing the correct interface card. Systems vary based on the wireless tools you are using, although you should be able to ifconfig to get your MAC address.

Once you have determined all your MAC addresses, log into your access point and input them into the MAC Filtering list. Once this is completed, enable MAC filtering and reboot your access point (most require a reboot for changes like this). Once this is done, you should be able to connect from the machines, which you have placed in the allowed list, but other computers not in the list will be denied. There is on caveat. Like with WEP, with the right skills and tools, someone can spoof, or forge, their MAC address. Not necessarily and easy thing to do, as they will have to spoof an ID that is in your list, but given enough time, someone could brute force it (in other words, iterate through a list trying all possible variations until they find one that works). However, this is not all that common, but it does happen.

Signal Control:

What do I mean by signal control? Controlling the strength of the signal that your access point sends out. This is simply a trial and error operation. Take a look at the documentation for your access point and determine how to change the signal strength. Once you have done this, log in to the access point administration tool and lower the signal a little. Now go to the outer edge of, or just outside the area where you will be using the wireless network. If the signal is still strong, lower the strength a little more. The idea here is to lower the strength of the signal to the point where it does not extend outside of your house, apartment, office, etc. This way, people on the outside cannot access your network without special equipment. 

Kill Broadcasts:

What I’m aiming at here is to set your access point so that it does not broadcast its SSID. An access point broadcasts its SSID by default. That’s why you can see that there is a wireless network available when you come into range of one. Most access points will allow you to turn this feature off. If this feature is off, the access point is, for all intents and purposes, invisible. Therefore, people can’t easily see that it even exists. The down side is that you will have to connect to the network manually by entering it’s name in the Airport utility or internet connect program, but that’s a small price to pay for the added security, at least it’s a small price for me to pay for a little extra security for my network.

Recap:

What basic steps can we take to help secure our wireless networks? Here’s a quick checklist:

  • Enable WEP encryption: Discourages the casual hacker
  • Enable MAC Filtering: Only allows known computers on the network
  • Adjust Signal Strength: Don’t use a signal that can be used outside of the building (office, apartment, etc). This is just asking someone to try and get on your network
  • Turn off SSID broadcasting: Run your network in invisible mode. Don’t show the whole world there is a wireless network at your location

These steps will help make your wireless network more secure. There are other things a person can do to make the network even more secure, such as using radius authentication with secure id cards, virtual private networks, etc. but this is not something that most home or small business users either want or can afford to do.

 
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