IT contractors should be advising firms not to use email accounts to store sensitive information, according to a major IT security company.

Many e-mail accounts hold things such as passwords and sensitive company data, as well as personal information and even receipts for things that have been bought, Symantec claims.

This data is then vulnerable to hackers, who by infiltrating one account with a spam email can have access to endless streams of business and personal information, according to the firm's product marketing director for Norton products Con Mallon.

"A lot of users have a track record of their activity, and they'll have receipts and details of sites they've brought things from. They'll have their CV. They'll have credentials of information," he said.

According to recent data from Symantec, spam accounted for 88 per cent of web traffic in 2009.

Meanwhile, Google claims that spam levels have continued to remain steady throughout the first quarter of 2010, despite the shut down of a number of major botnets.