The next major computer virus attack could cost SMEs as much as £2.1bn, according to new research conducted by McAfee Security.

McAfee's study revealed that 70 percent of SMEs had received at least one virus over the past year. All had lost money (around £843 per company) and were subjected to downtime amounting to an average of around one lost working day as a result.

But with numerous antivirus solutions available and the huge amount of media publicity, many companies still haven't installed such software and those that have simply do not bother to keep it up to date. In fact, only half of respondents regularly rescheduled virus scanning of company computers.

"It is very important that SMEs protect themselves against cybercrime properly," said Marc Vos of McAfee. "Although many have protection, its is useless unless they keep it up to date."

"Viruses tend to grab news headlines but SMEs are often left open to other forms of cybercrime such as fraud or hacking. Virus and firewall protection are absolutely essential for any computer use," added Vos.

Despite their lack of protection, nearly all respondents (91 percent) felt that cybercrime is on the increase.

"Viruses or hacker attacks could be disastrous for many SMEs; they must start putting protection in place," said Peter Scargill, IT chairman of the Federation of Small Businesses.