Old-school viruses pose biggest corporate threat

XM/Laroux, a macro virus which attacks spreadsheet programs, was the most commonly reported virus in 1999, despite being over three years old.

Sophos' annual virus report showed old viruses still pose the greatest threat to corporate networks; with the ten-year-old Form boot sector virus also appearing in the top ten.

But according to Sophos, self-propagating viruses like ExploreZip, Melissa and Ska-Happy99 are becoming more frequent. Their ability to spread globally via email within days makes them an even greater threat, the company claimed.