Tips to Secure Your Small Business Wi-Fi Network

• By Eric Geier
• Jul 21, 2009
• Article is provided courtesy of Cisco Press

From the author of
Wi-Fi Hotspots: Setting Up Public Wireless Internet Access

Securing your wireless network is all about layers. Flipping on encryption helps block people from connecting over Wi-Fi and also scrambles the network traffic that flows through the air. However, this doesn’t help if someone can just come into the building and plug in. Plus, if the encryption key is cracked, you’re toasted. Though encryption is the most important security layer for wireless networks, you need to use more. The more techniques you use, the more secure your network and its data will be.

The following tips describe many techniques and methods to secure your small business Wi-Fi network.

Use WPA Encryption — preferably WPA2

The Wired Equivalent Privacy (WEP) encryption method was debunked long ago and provides inadequate Wi-Fi security. The WEP encryption keys can be cracked, in some cases, within minutes. You should use the Wi-Fi Protected Access (WPA or WPA2) encryption method.

The first WPA version, which uses the Temporal Key Integrity Protocol (TKIP) algorithm, has also become vulnerable recently. However, WPA’s weaknesses aren’t as bad as WEP’s (yet) and using strong passphrases can help. Nevertheless, if the computers and networking gear support WPA2 with the Advanced Encryption Standard (AES) algorithm, use it.

Use the Enterprise version of WPA/WPA2

To prevent employees from seeing the encryption keys or passphrases and having them loaded on their computers, you should use the Enterprise version of WPA or WPA2 rather than the Pre Shared Key (PSK) or personal version. Otherwise, when an employee leaves the company, he or she will still have the key to unlock the network. Additionally, their laptop could be stolen and a thief could have the key. Sure you can change the encryption settings, but it’s a headache. WPA/WPA2-Enterprise hides the actual encryption key; it’s never loaded onto the computers. After everything is configured, users log onto the network with a username and password that can be changed or revoked.

WPA/WPA2-Enterprise requires a RADIUS server, which provides the management of the user accounts. There are RADIUS servers targeted toward small businesses such as Elektron and ClearBox, which cost $600 to $700. To save money, you might want to opt for a service that hosts the server for you such as WiTopia, which runs for $99 a year. Another option is to purchase an access point that has a simple built-in RADIUS server such as ZyXEL’s NWA-3160, which sells for as low as $140 online.

Secure Ethernet Ports

Though you can use the latest and greatest Wi-Fi encryption in the world, it’s useless if someone plugs into a port within the building and can access the network. Additionally, employees could even plug their own AP into a port, intentionally or not, giving out open wireless access. To reduce the chances of this happening, make sure all routers, APs, and network devices are hidden and secure. You could use closets, high mounting locations, or the space above false ceilings.

For more wired network security, you could use 802.1X authentication if you have the business-class gear that supports it. Using MAC address filtering on the network also helps to prevent authorized users from accessing the network. However, neither of these methods will hide the traffic from eavesdroppers on the wired network — review the next tip.

Use Extra Encryption (VPNs)

To encrypt the wired side of the network and for double Wi-Fi encryption, you could use VPNs. You could buy a standalone VPN server, install server software on a computer, or purchase a hosted service. Every computer on the network could be configured to connect with the VPN server. Then even the users’ traffic on the wired side of the network will be encrypted and double encrypted over the airwaves.

Don’t Connect to Other Networks

Since computers may be sharing files or have sensitive data on them, you need to prevent them from connecting to other networks. Check Windows to make sure it isn’t set to auto connect to available networks. In Vista, you can even use the WLAN commands for the Netsh utility to block all networks but yours. This would prevent employees that mistakenly or intentionally connect to neighboring networks.

Separate Traffic with VLANs

Dividing your network into separate virtual networks (VLAN) provides internal security. You can better control the resources and network traffic employees can access and receive. Thus, a regular employee can’t open files shared on the computers of the management staff. Additionally, if an employee does monitor the raw network traffic, he or she will only see traffic on their own virtual network. VLANs can also provide external security as unauthenticated users can be allocated to a separate VLAN. Plus, if someone does gain unauthorized access, he or she will have access to only a portion of a network.

Secure Shared Folders and NAS Devices

To control the exact files and resources employees can access, verify the folder sharing permissions and the NTFS permissions of files and folders. Additionally, configure sharing settings for any network drives or NAS (network attached storage) devices. Plus, configuring these settings helps prevent access of files from unauthorized users.

Verify Firewalls

To protect the network from Internet or local attacks and intrusions, you should always have firewalls running on the computers and on the network router. Ports should only be opened only when necessary. For additional security, you can define the IP address scope that can use the ports.

Use MAC Address Filtering

Though Wi-Fi hackers can easily spoof the MAC addresses of their network adapters, using MAC address filtering provides another layer of security. It just takes some overhead to enter the MAC addresses of all your computers or devices.

Disable SSID Broadcasting

Though not broadcasting your network name only throws Wi-Fi hackers off for a moment, it does add another layer of security. The SSID can still be retrieved over a short period of time with basic tools. Additionally, hiding the SSID can cause a big headache for you; it can cause connectivity problems.

Keep Hardware Updated

Securing your network and computers requires some maintenance. You need to periodically check for firmware updates for the router, access points, and other network components. You also need to keep track of the network adapters that are loaded in the computers and update them with new drivers if and when they become available. Additionally, make sure the operating systems on all the machines are kept update-to-date with security patches and fixes. Keeping everything maintained will help ensure any known vulnerabilities are addressed and any new security features are supported.

Keep Wi-Fi Signals Contained

If you could completely block incoming and outgoing radio signals at the exterior walls of your building, you wouldn’t have to worry about Wi-Fi attackers or eavesdroppers in the parking lot. Though that isn’t practical, you could try to reduce signal leakage. Between relocating APs and tuning down their power levels, you can somewhat keep the signals contained in your controlled area.