London Underground has announced plans to extend Wi-Fi access at tube stations after a successful trial at Charing Cross.

Tube travellers have been able to access BT Openzone’s Wi-Fi at Charing Cross Tube station since November, as part of a six-month trial. According to a London Underground survey, more than half of passengers believed that access to Wi-Fi would improve their experience of the Tube.

However, experts have raised concerns around the security and performance of the network.

London Underground hopes to extend the service to up to 120 tube station platforms, not the trains, by 2012, and is calling for telecoms companies to bid for a contract to deliver the Wi-Fi access. The contract is expected to be awarded by the end of 2011.

The winning bidder will start by extending the Wi-Fi service currently used by London Underground staff at 16 stations, to passengers.

Boris Johnson, the Mayor of London, said: “The roll out of Wi-Fi technology across the platforms and public areas of our Tube stations will finally allow Londoners to use mobile devices to pick up their emails, access social media sites and stay in touch with the world above while they traverse our subterranean transport network.

'We are inviting companies to bid to do this before next June.”

London Underground’s invitation to tender also calls for bidders to supply details of how they would establish a street-level Wi-Fi network, for example, at bus shelters.

Having provided the Wi-Fi access at Charing Cross for the trial, BT said "it will actively review any invitation to tender to the London Underground network Wi-Fi tender.”

According to experts, however, London Underground needs to address security and performance concerns in the rollout.

Professor John Walker from the London Chapter ISACA Security Advisory Group, said: "Wi-Fi on the underground presents a number of security challenges, ranging from misuse by the anarchist, and adversaries of society, through to personal exposure, and compromise born out of criminality, and hacking.

"The more serious potential is of course relating to terrorism. Clearly, where one has a communicating network underground, it holds an increased level of threat in which this helpful technology could be exploited, and abused to muster a much more effective and wider bomb attack on the underground."

Michael Lynch, head of identity protection at card protection company CPP, said that there is always a risk when connecting to a public Wi-Fi system. 

“If a criminal sets up their own ‘BT Openzone’ and mobile devices are set to connect to (that zone) automatically, it enables [criminals] to see everything a passenger accesses on the Internet, for example, if they log into their online bank.”

Lynch said that passengers can avoid this risk by changing their mobile device’s settings to not automatically connect to Wi-Fi networks.

Stephen Rayment, CTO of wireless networking solutions company, BelAir Networks, added that the network could be further secured by ensuring that policy enforcement is performed in each Wi-Fi access point, rather than at a controller or gateway.

A spokesperson for Transport for London (TfL), said: "Access to mobile and data networks is already common on many world metros and our customers tell us they would welcome this.

"The majority of the Underground is actually above ground where customers can already use mobile and data services. LU has tried and tested procedures in place to deal with unattended items on the Tube."

But Rayment believes that performance on the Wi-Fi network is an even bigger concern than security.

“During peak times, there can easily be hundreds of people at a tube station. Delivering sufficient data capacity in these high interference environments is critical. If people have a hard time using the service because it keeps dropping out, they’ll soon turn off.”

Meanwhile, TfL is holding ongoing talks about the potential provision of mobile phone services on the Tube with mobile phone operators and other suppliers.

It said that any solution would need to be funded through mobile operators with “no cost to fare or taxpayers”.

In March 2009, TfL scrapped a plan to trial mobile phone use on the tube network due to high costs.