The majority of businesses are leaving their computer systems open to denial of service (DoS) attacks because of widespread ignorance about the threat, according to new research.

Email filtering vendor intY said a survey of UK businesses found that more than half failed to take adequate protection measures against denial of service attacks – where computer systems are bombarded with traffic in an attempt to bring them down – because they were unaware of the risk.

"Most people think of online gambling websites when they think of DoS attacks, however all businesses need to realise that they could easily be attacked through email," said Mark Herbert, founder of intY.

Most businesses currently filter email at the desktop or network level, but do not require their Internet Service Provider (ISP) to filter Internet traffic – a step that would reduce the strain on the organisation's firewall.

Herbet warned that email-based DoS attacks were particularly troublesome as it is difficult to separate legitimate traffic from attack traffic. He said that earlier this year the Greater Manchester Police saw its email system crippled after its chief constable was bombarded with 2,000 emails an hour.