Wireless networks offer convenience and low cost, but they do not come with enterprise-class security out of the box. The ease of use that has made wireless LAN technology based around the 802.11b standard so popular also makes it easy for outsiders to listen in to data traffic.

Businesses that want to make successful use of a wireless LAN need to design for security from the outset. The reach of wireless LAN signals easily extends beyond a building, and even the WiFi card that comes as standard with many laptops will pass through walls.

A casual passer-by with a laptop or PDA can use these signals to gain access to the network. There is no need for the hacker to enter a building to listen in to traffic. A wireless LAN card and some special 'sniffer' software, which is easy enough to locate on the web, provides all the tools needed to snoop on a wireless LAN.

To avoid security breaches, companies need to lock down their wireless networks with both encryption and access management.

Access management, such as setting network passwords and restricting use of the network, for example by checking connected machines' MAC addresses against an authorised list, will do much to deter free loaders. Even a simple password or setting up the wireless LAN so that it does not broadcast its name (or SSID) will make life harder for war chalkers.

But companies also need to ensure that their wireless LANs do not allow back door access to sensitive information, by putting access controls on to databases and, possibly, by using wireless together with a virtual private network. In some cases, putting the wireless LAN outside the firewall might be appropriate.

Companies can also deter snoopers by turning on the basic WEP encryption or more sophisticated methods such as LEAP and the 802.11x standard. And once all this is done, businesses need to set up robust policies to deal with unauthorised access points.

Wireless networking brings clear benefits in terms of staff productivity. Securing a wireless LAN is not difficult, but it needs to be part of the plan from the outset.