Companies have failed to learn the lessons from last year's damaging Love Bug virus, analysts said.
The self-replicating virus, which sent itself to every address book entry when opened, was attached to an e-mail titled "check this out" which promised pictures of tennis star Kournikova. It is thought to have originated from an ISP address in the Netherlands.
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As well as mass mailing from an infected system which overloaded communication channels, the Kournikova virus activated the default Internet browser and directed it to the Web site of Dynabyte, a Dutch computer reseller. A Dynabyte spokesman said the virus did not seriously affect business, but that the company was investigating reports that the virus had been launched by a disgruntled former employee.
Last year, the Love Bug virus caused an estimated $10bn (£6.7bn) in lost business productivity, according to US-based analysts.
"To give an idea of the scale of this thing, one company received 4,500 of these [Kournikova] e-mails overnight outside office hours," said Graham Cluley, senior technology officer at Sophos Anti-Virus.
Cluley advised that firms set up an e-mail gateway stopping any double extension or VBS file - the Kournikova virus had a JPeg and VBS file attached - "whether they are viruses or not".
"Companies do not do enough to emphasise the importance of security," said Tony Lock, an analyst at Bloor Research.