There were 237 million hacking attacks from January to June this year, a 50 per cent increase over the previous half year, research shows.

IBM's Global Business Security Index shows one in 52 emails contained a malicious security threat in December 2004,a figure that increased to one in 28 by June this year.

There was however a fall in the ratio between spam and legitimate email from 83 per cent in January to 67 per cent in June, but virus carrying emails increased by 50 per cent.

The IBM report also records a 10-fold increase in what it calls ‘spear-phishing’, the deliberate targeting of individuals or organisations in an attempt to trick them into giving away sensitive information.

Other findings in the Global Business Security Index include: