The study, carried out by IT security firm Sophos, indicates the level of unwanted messages rose to 96.5 per cent of all business email in June this year, up from 92.3 per cent in the first three months of 2008.

Graham Cluley, senior technology consultant for the firm, said companies now need to have an effective anti-spam defence in place in order to do business on the internet.

He added: "It should be remembered also that some spam is not just a nuisance, but malicious in its intent - trying to get you to click on an attached Trojan horse or lead you to a dangerous website."

Mr Cluley went on to say anti-spam and anti-malware solutions should be updated around the clock so they can handle the latest internet attacks.

Last week, online security firm BitDefender identified a new malware attack which attempts to trick internet users into downloading and installing malicious software via a fake news report of a US army strike against Iran.


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