Securing your wireless network
- By Bob Brewin, Florence Olsen
- Nov 07, 2004
Earlier this year, the Homeland Security Department's inspector general chided department officials for broadcasting wireless signals from a Bureau of Citizenship and Immigration Services building into an adjacent parking lot and surrounding public roads and residences.
DHS officials have corrected that and some other wireless security problems cited in the inspector general's report. Officials at DHS and other federal agencies are required to follow security guidelines that National Institute of Standards and Technology officials have developed
for preventing electronic eavesdropping on unclassified wireless networks.
The NIST guidelines warn that wireless communications are inherently open to intruders. Any wireless communication is effectively "an Ethernet port in the parking lot," authors Tom Karygiannis and Les Owens state in the introduction to the guidelines, known as NIST Special Publication 800-48.
The guidelines are useful in helping federal agency officials reduce data theft and other information security risks associated with using 802.11 wireless local-area networks, Bluetooth wireless networks and handheld messaging devices such as Research in Motion Ltd. BlackBerrys.
NIST's guidelines are a reminder that significant effort, resources and vigilance are required to maintain security controls on wireless communications.
The following are recommendations for securing wireless networks:
Set strict policies
Set sound policies for network configuration and design and for strong authentication and encryption standards.
Maintain a complete inventory of all access points and 802.11 wireless devices.
Only allow users with devices that conform to authentication and security policies to access the
Wi-Fi network. This keeps out sniffers and hackers looking
to exploit open networks.
Provide boundary protection around agency buildings.
Position wireless access points in the interior of buildings instead of near exterior walls and windows.
Install a properly configured firewall between the wired and wireless networks.
Don't advertise your Wi-Fi presence
Turn off the Service Set Identifier (SSID), which is a beacon that broadcasts the presence of Wi-Fi access points. If left on, choose a vanilla SSID that does not readily identify the agency or company.
Turn off wireless access points if they are not being used after-hours or on weekends.
Barricade the bridge
Cripple Wi-Fi functions of laptops or PDAs when connected to a wired network. Otherwise, the Wi-Fi card could serve as a bridge between a wireless hacker and the wired network.
Disable file sharing on wireless laptops and handheld devices.
Disable the ad hoc mode for 802.11 networks.
Disable the Dynamic Host Configuration Protocol and use static IP addressing instead.
Use strong authentication
Wired Equivalent Privacy (WEP), the lowest level of Wi-Fi authentication, can be breached with a dictionary attack that can capture keys. Use the 802.1x standard built into Windows XP, which provides a new key for every session.
Change the default keys for WEP to minimize the risk of unauthorized log-in attempts.
Use strong encryption
Follow the Defense Department's lead and mandate use of the new NIST Federal Information Processing Standard 140-2 Advanced Encryption Standard. Provide more defense by using a virtual private network client in addition to the standard.
Monitor the airwaves
Use radio frequency tools such as the free and open-source Kismet software or premises-based sensing services offered by companies such as AirDefense Inc. to routinely sniff for the presence of rogue Wi-Fi access points or unauthorized clients. Periodically test access point boundaries to measure the reach of their wireless coverage.
Deploy intrusion-detection agents on wireless networks to detect unauthorized access and activity.