Software giant Microsoft is facing legal action from a group of US lawyers who believe the company's Windows operating system is a "global security risk".
Some viruses have posed as messages from Microsoft
The group behind the lawsuit, filed in California, want PC users who have suffered losses as a result of identity theft or during the recent spate of viruses to take action against Windows.
At the heart of the case is the licence that Microsoft - together with most other software firms - impose on users, which is designed to relieve the maker of any responsibility for damage or loss caused as a result of using the software.
Should the case make headway, far-reaching - and potentially expensive - changes to the computer industry's business practices could be the result.
"This represents the first salvo for consumers to say to software makers: wait a second if you are going to put out software that needs patching three times a week, take responsibility for it," said Mark Rasch, former head of the US Justice Department's Computer Crime unit.
The case has a long way to go before it gets anywhere near that stage, however.
At present only one person has signed up: a 50-year-old Californian woman who had her social security number and bank details stolen over the Internet.
Sales: $32.2bn (£19.3bn)
Profit: $10bn (£6bn)
Cash hoard: $49bn (£29.4bn)
(Figures for year to June 2003)
Microsoft insists the case is without merit.
"This complaint misses the point," a spokeswoman said.
"The problems caused by viruses are the result of criminal acts by people who write viruses."
But the lawsuit claims that Microsoft is liable because the "patches" it issues to repair flaws in its software are so complex and time-consuming to install that they only serve to tell virus-writers and computer criminals what loopholes to look for.
"Microsoft's eclipsing dominance in desktop software has created a global security risk," the lawsuit says.
"As a result of Microsoft's concerted effort to strengthen and expand its monopolies and by tightly integrating applications with its operating system... the world's computer networks are now susceptible to massive, cascading failure."
The case comes at a time when successive viruses have crippled several Microsoft-based systems, denting the productivity of many workplaces.
It also comes amid growing criticism in some parts of the technology world of what is termed the "monoculture" caused by Microsoft's near-monopoly over desktop systems.
The company was found to have abused its monopoly in a US government lawsuit in 2000, but suffered only minor punishment.
But the European Commission is edging closer to concluding its own case against the software firm.