A survey commissioned by managed email company intY also shows that half of U.K. companies use desktop or network gateway spam filtering which can be open to DoS attacks.
"Even the Greater Manchester Police has fallen victim to an email DoS attack. Earlier this year its chief constable was bombarded with 2,000 emails per hour by cyber criminals in an attempt to crash the force's computer systems," said Mark Herbert, founder of intY. "Businesses need to realise that it could happen to them too. It is worrying that so many organisations have their heads in the sand and don't realise they are vulnerable to attacks that could potentially bring their businesses to a standstill."
The research also revealed a hidden anger at ISPs, with 92 percent of respondents claiming that that their service providers are not doing enough to prevent the onslaught of spam and viruses on company networks.
In August SC reported hidden email attacks are hitting company networks without ever intending to actually appear within inboxes.
"While email DoS attacks are quite new, they are increasing and slowly making headlines," said Herbert. "Most people think of online gambling websites when they think of targets of DoS attacks, however all businesses need to realise that they could easily be attacked through email. It's a danger facing us all."