Second Life , the popular virtual world, is being targeted by IT administrators who want to stop staff using up bandwidth by playing the game at work. Security firm Sophos said several big companies had requested the ability to block access to Second Life through their corporate networks.

Graham Cluley, senior technology consultant at Sophos, said: "People get addicted to these online games. We're not saying that the game is bad but there's a time and a place for it."

More than 90 per cent of IT administrators polled by Sophos said they wanted to block network access to games at work as they drain the company bandwidth, as well as waste time at work.

With over one million users and some 4.8 million 'residents', Second Life is one of the most popular applications Sophos will allow network administrators to block through its anti-virus software. Online games such as Everquest and Lineage are also off limits.

Web security firm ScanSafe today released data showing that almost half of all traffic on corporate networks is non-work-related. Its latest Global Threat Report showed that 49 per cent of the web traffic scanned in February was non-productive, including requests for gambling, music, porn and webmail sites.