The number of spam messages jumped to a record 94 per cent of all email on the internet last month, research from Postini reveals.
More than 25 billion spam messages were blocked in December, an increase of 144 per cent from the previous year.
This rise in spam is linked to a virus released by hackers in late December, called the ‘Happy New Year' worm, which infected high numbers of computers with botnets and then pumped out spam, experts at the email management company claim.
The worm, also known as Nuwar and Mixor, was hidden in electronic postcards posing as greetings from friends and family. This widespread attack drove the daily number of email-borne viruses up 20-fold across the New Year weekend.
"This continued rise in spam levels is threatening the viability of email for businesses that are not properly protected," warned Daniel Druker, executive vice-president of marketing at Postini.
"Just 15 minutes per day dealing with the increased volume of spam can cost companies £1,600 per employee per year, which adds up to tens of billions of pounds of lost productivity around the world."