As many as a quarter of business wireless local area networks (WLANs) don't encrypt their traffic.

That includes the much-maligned Wireless Equivalency Protocol (WEP) as security, according to a new survey released by specialist firm RSA Security.

The RSA report points out that users could easily connect to an unsecured business WLAN rather than a wireless hotspot - either on purpose or accidentally - opening the organisation up to serious risks such as data theft, identity theft or attacks such as denial of service.

Tom de Jongh, product manager of SafeBoot, said: "It is a very dangerous risk to take and it is yet another area where businesses are not showing enough common sense when it comes to security.

"If it was impossible and prohibitively expensive to protect the WLAN, then you could understand why almost a quarter were failing to do so.

"But there are plenty of cost-effective products out there that will encrypt traffic and ensure that prying eyes, even if they get access to the network, won't then be able to see the data passing through it.

"In London, the number of wireless access points grew by 160 per cent last year, so there has to be greater protection put in place."

He added: "Protect your Virtual Private Network by using content and/or device encryption that will ensure that data passing through the secure VPN and the data stored on the user's laptop will always be protected. Another is enabling security that allows secure authentication to build up the VPN tunnels.

"If businesses want to be the next Marks & Spencer or Nationwide - who have both been burnt by laptop thefts - then they should carry on ignoring their WLANs.

"If they want to be a safe, secure company that protects its assets, then it should follow our advice and start looking into proper security."