CAMBRIDGE -- Dan Geer lost his job but gained his audience. The very idea that got the computer security specialist fired has sparked serious debate in information technology. The idea, borrowed from biology, is that Microsoft Corp. has nurtured a software "monoculture" that threatens global computer security.
Geer and others believe Microsoft's software is so dangerously pervasive that a virus capable of exploiting a single flaw in its operating systems could wreak havoc.
Just this past week, Microsoft warned customers about security problems that independent experts called among the most serious yet disclosed.
After he argued in a paper published last fall that the monoculture amplifies online threats, Geer was fired by security firm @stake Inc., which has had Microsoft as a major client.
Geer insists there's been a silver lining to his dismissal. Once it got discussed on Slashdot.org and other online forums, the debate about Microsoft's ubiquity gained in prominence.
"No matter where I look I seem to be stumbling over the phrase `monoculture' or some analog of it," Geer, 53, said in a recent interview in his Cambridge home.
In biology, species with little genetic variation -- or "monocultures" -- are the most vulnerable to catastrophic epidemics. Species that share a single fatal flaw could be wiped out by a virus that can exploit that flaw. Genetic diversity increases the chances that at least some of the species will survive every attack.
"When in doubt, I think of, `How does nature work?' " said Geer, who has a doctorate in biostatistics from Harvard University.
"Which leads you, when you think about shared risk, to think about monoculture, which leads you to think about epidemic, he said. "Because the idea of an epidemic is not radically different from what we're talking about with the Internet."
Geer isn't the first to argue that the dominance and tight integration of Microsoft operating systems and software makes the global computing ecosystem vulnerable to a cascading failure.
Geer's paper did little more than make the point with particular fervor -- which only intensified when Geer was fired.
"The hoopla around him losing his job gave the story some extra frisson," said Internet security expert Bruce Schneier, a coauthor of Geer's.
Microsoft, which denies pressuring @stake to fire Geer, says the comparison between computers and living organisms works only so well.
"Once you start down the road with that analogy, you get stuck in it," said Scott Charney, chief security strategist for Redmond, Wash.-based Microsoft.
Charney says more use of the Linux open-source operating system, a rival to Microsoft Windows, might create a "duoculture," but that wouldn't deter sophisticated hackers.
True diversity, Charney said, would require thousands of different operating systems, which would make integrating computer systems and networks virtually impossible. Without a Microsoft monoculture, he said, much of the progress in information technology could not have happened.
Another difference: computers can be unplugged and rebooted; organisms cannot.
The theory also has skeptics outside of Microsoft.
Security consultant Marcus Ranum has emphasized that many network threats have little to do with the vulnerabilites of monoculture. Planting three strains of corn offers insurance against some diseases, he notes, but without a fence, deer will eat all three.
But Ranum also says the monoculture story "would barely be news" if @stake "hadn't done a brilliant surgical marketing strike on its left foot by firing Dan."
At an October hearing of the House Government Reform Committee's technology subcommittee, Steven Cooper -- the Homeland Security Department's chief information officer -- was questioned about the federal government's vulnerability to monoculture.
Cooper acknowledged it was a concern and said the department would likely expand its use of Linux and Unix as a precaution.
The monoculture idea is also influencing how experts look for solutions to security problems.
Mike Reiter of Carnegie Mellon University and Stephanie Forrest, a University of New Mexico biologist who has been gleaning lessons for computer security from living organisms for years, recently received a $750,000 National Science Foundation grant to study methods to automatically diversify software code.
Daniel DuVarney and R. Sekar of the State University of New York-Stony Brook are exploring "benign mutations" that would diversify software, preserving the functional portions of code but shaking up the nonfunctional portions that are often targeted by viruses.
Geer -- who now consults, lectures, and works with a start-up -- also believes monoculture theory points the way to possible solutions. But those solutions are dramatic, and haven't always been followed. They would require, for example, banning from the Internet computers whose software hasn't been updated with the latest antivirus patches.
Geer doesn't believe breaking up Microsoft is the answer, even though his paper was published by the Computer and Communications Industry Association, which aggressively backed the antitrust case that tried to split up the company.
But Geer says the company should disentangle its tightly integrated products, such as Microsoft Word and Outlook.
Microsoft contends, as it did during its antitrust trial, that the integration of those products is the heart of what it offers consumers.
Still, Microsoft's Charney doesn't entirely dismiss the idea of examining computer security through a biological lens. "Although biodiversity-monoculture issues may be more complex than people have been thinking about them, it does not mean you can't learn from it and draw some parallels," he said.
Geer calls such comments proof the idea is resonating.
"You see Microsoft talking about it," he said, "when before, they didn't."