Cyber attacks on the UK have reached "disturbing" levels, according to Ian Lobban, director of communications intelligence agency GCHQ.
The attacks are targeting sensitive data on government computers and defence, technology and engineering firms' designs, he said in The Times.
"Such intellectual property theft doesn't just cost the companies concerned; it represents an attack on the UK's continued economic wellbeing," he said.
Lobban's revelations come just ahead of the London Conference on Cyberspace on 1 and 2 November hosted by foreign secretary William Hague.
The conference will bring together representatives of governments, civil society and business, including US secretary of state Hillary Clinton, European commissioner for the digital agenda, Neelie Kroes, and Wikipedia founder Jimmy Wales.
Announcing the conference, Hague said no one government or country has the answers.
"Together we must begin to address how we can maintain the economic and social benefits of the internet and guard against the criminal and security cyber threats without suffocating future innovation," he said.
The conference will focus on economic growth and development, social benefits, cyber crime, safe and reliable access, and international security.
The UK cyber strategy, expected to be released in mid-November, is also aimed at enabling the UK to reap the huge economic and social value of a resilient and secure cyber space by 2015.
Making the UK more resilient to cyber attack and better able to protect its interests is one of the key elements of the strategy, Owen Pengelly, deputy director of policy at the Office for Cyber Security and Information Assurance in the Cabinet Office told a recent Trusted Computing seminar in London.