Business networks are being dominated by bandwidth-zapping social networking sites.

According to Network Box, accessing and downloading material from Facebook and YouTube when at work accounts for more corporate web activity and used bandwidth than any other sites. It detected that nearly six per cent of all web traffic from business networks is to Facebook – higher than to any other website while nearly eight per cent of all corporate bandwidth is taken up downloading YouTube videos.

In terms of bandwidth, the rest of the top five were Facebook (4.4 per cent), Windows Updates (3.8 per cent), Yahoo's image server Yimg with 2.8 per cent and Google with 2.7 per cent.

Simon Heron, internet analyst for Network Box, said: “It is important that businesses use this information to set user policies and update security systems. IT teams must ensure employees only download files from safe sources, and educate them on the threat of malware from social sites.

“Interestingly, Windows Updates are the third heaviest user of bandwidth after YouTube – nearly four per cent of corporate bandwidth is being used just to fix software problems on Windows.”