Firms rely on the internet too much and must make sure they have a business continuity plan in place to deal with any prolonged outage, the government has warned.

In its first National Security Strategy publication, the cabinet office warned that more than 50 per cent of the UK's economy is exposed to the threat of cyber-attacks.

The report said: "As economies and societies grow increasingly dependent on national and global electronic information and communications systems, it becomes even more important to manage the risk of disruption to their integrity through cyber attack, whether terrorist, criminal or state-led."

It pointed out the internet-based attacks on Estonia last year which led to widespread web outages.

The report also deals with the threat to the UK from terrorism, nuclear attack and natural disasters.

A recent survey for Connect found that one in ten companies has lost important data as a result of a backup failure. The company has now developed a unique online backup service - http://www.totalrecall.co.uk – for SMEs to ensure they can survive any disaster.