Is Your Wireless Network Secure?

Posted on Monday, November 08, 2004 @ 12:14:12 CST in General
by kguske

You lock the door and turn on the alarm, thinking your home is safe. But if you have an unsecured wireless network, think again. Read more to understand the problems, risks, technologies and solutions for securing wireless networks.
On a recent drive around our neighborhood, we found that two-thirds of the wireless networks were open for anyone to use (see the sample map to the right, where red represents a secured network, green represents an unsecured network, and street names have been blurred to protect the unsecured). A similar drive through an office / commercial area identified several open business networks, proving it's not just a problem for homeowners.

Scanning for wireless networks by driving around is called "wardriving" or "stumbling." According to Eric Vandevelde in "The Origin and Legality of Warchalking," "The name for the practice of finding wi-fi hotspots comes from the 1983 movie War Games where a teenage Matthew Broderick hacked into military computers at NORAD by wardialing random phone numbers using a modem. The terms nowadays are wardriving, warwalking, and warflying-each variation reflecting the means of conveyance by which warchalkers search out, find, and mark down publicly accessible hotspots....Once they find a network, they use chalk to mark the location of the hotspot as well as the network type, name, and bandwidth." Warchalking, or marking symbols (see symbols below) on buildings with wireless networks, is common in large urban areas.

But it's not limited to urban areas, and although mapping wireless networks may sound illegal, it isn't, argues attorney Patrick Ryan in the Virginia Journal of Law & Technology. However, actually connecting to an unsecured network might be illegal and using another's wireless network to send spam or commit other crimes definitely is, and there have already been convictions. There are legitimate purposes for it such as surveying a site to determine the best place to put wireless access point for maximum coverage, which is common in large stores or warehouses and even some offices. By understanding the risks and how the technologies work, you can prevent the majority of unauthorized access very easily using free software.

What are the risks?

Most likely, unauthorized access to a home network is accidental. On a recent visit, my father accidentally connected to our neighbors' wireless network thinking it was ours. That happens because, by default, a computer with a wireless adapter will automatically connect to the first open wireless network it can find. There are two risks when this happens: access to personal information and the use of the network's resources in inappropriate ways.

Most home users don't share file directories or printers, so it's unlikely that an unauthorized user will be able to directly access personal information stored on your computer. However, because the user has access to your wireless network, (s)he can use your Internet bandwidth, slowing down your access. But the real problem would occur if someone used your network to send spam or perform other illegal activities. The police can identify your network by its Internet address and, although they understand that wireless networks can be compromised, they wil still visit you first.

How does it work?

To identify open wireless networks, you need a laptop, a standard wireless network adapter, scanning software, and, if you want to map the locations of wireless networks, a global positioning system (GPS). It's easy to find free software for scanning wireless networks. Wireless adapters cost $10 to $60, depending on the performance and range, which can be several hundred yards. Although you can convert the results for use with mapping software like DeLorme Street Atlas or Microsoft Mappoint, you can generate a detailed map for free by uploading a scan file to a web site. The whole process of mapping the wireless networks in our neighborhood (about 230 homes) took less than 10 minutes.

The scanning software shows information about each wireless network, including the name, the wireless channel, speed, hardware manufacturer, Internet (IP) address, signal strength, latitude and longitude, and the type of encryption, if any, used to secure the network. We found that most network names aren't changed from the default name, and Linksys is the most popular wireless router in our neighborhood.

If a wireless network is not secured, anyone with a wireless PC in range can connect and use the network's shared resources, including the Internet connection and any other resources that are shared like printers and hard drives. This means that someone could access any files stored on a shared directory, though most home users don't use this capability. It is more likely that an unauthorized person would use the shared Internet connection that is set up by default in the wireless router or access point - the hardware that enables wireless networking.

What should I do?

The easiest way to prevent unauthorized wireless access is to set up wireless encryption on the router or access point. The most common form, Wired Equivalent Privacy (WEP), isn't foolproof. Unfortunately, free software can be used to break WEP codes, but it takes persistence and time, so it isn't really practical. To set up WEP, enter a cryptic password in your wireless access point or router, then enter the same password in the wireless adapter configuration on each computer that will connect to your network. There are two types of WEP encryption - 64-bit and 128-bit. Since 128-bit requires 16 more characters in the password, it is more difficult to break. Make sure the wireless network works correctly with all computers before turning on encryption, though, so you can more quickly resolve other potential connection problems before adding encryption to the mix.

WEP encryption is not the only way to protect a wireless network. More advanced encryption technologies are available, though less commonly used, including Wi-Fi Protected Access (WPA) and, eventually, WPA version 2. Many wireless routers can also be configured to allow connections only from specific computers using Media Access Control (MAC) Authentication. A MAC address is assigned by the manufacturer of the network adapter and uniquely identifies each node of a network. The MAC addressed can be overridden (or "spoofed") using software, but the number of possible MAC addresses from which to guess is staggering. Specifying which MAC addresses can connect to a wireless network adds another layer of protection against unauthorized access and can be used in addition to wireless encryption.

Most wireless routers and access points have a built-in firewall that prevents unauthorized access to the network from the Internet, but won't block a wireless connection which is on the network, behind the firewall. Fortunately, there are a number of really good, free programs to provide all types of security, so you won't have to pay to get really good protection for all the computers on your wireless network. Some companies pay thousands for software to analyze wireless networks, but you can get free software to do this, too. Beware of expensive software that monitors for wardrivers, though, since this approach requires a computer to be turned on all the time (many people leave the wireless router on, but shut down their PCs when not in use). Frequently, these utilities notify you of unauthorized access but can't prevent it, so they're only useful IF your computer is on and IF you're available to react when a breach occurs. Most routers log access to the network anyway, so you can check there for anything suspicious.

This brings up an additional approach for protecting wireless networks: simply turn off wireless access when it isn't being used. You can do this by unplugging the router or access point (e.g. when you are away on vacation) or by turning off all wireless access in the configuration (e.g. overnight while you sleep or during the day while you are away). And unless you leave the door unlocked, there is no way to get around this approach.

Thanks, Neighbor

There are multiple ways to protect wireless networks from unauthorized access. Wireless encryption, MAC authentication, and free security software can be used together in a multi-pronged approach, but even using only one of these is better than leaving your wireless network unsecured. By the way, I thanked my neighbor for sharing his bandwidth with my father, then helped him secure his wireless network.

Copyright 2004 by Kevin Guske, All Rights Reserved.