Worm activity fell last month by over 80 per cent, according to research released today.

A study by managed email provider Frontbridge Technologies found that 319 million of the emails it handled in May were infected with some kind of internet worm, but that the figure dropped to 36 million in June.

"Despite a lull in activity last month, we still warn companies that the danger of viruses remains ever present," said Charles McColgan, chief technology officer at Frontbridge.

"We continue to see new virus strains transmitted across our network on a daily basis."

The company attributed the fall to a decline in mass mailing worms such as Sasser, but reported a rise in Trojan software that allows remote access to infected PCs.

One particularly nasty variant, Fantibag Trojan, blocks access to a range of security websites.