<p>Of course, Microsoft is the biggest of targets for computer criminals. But it's not just size that's the issue here, Butler says. "Microsoft's leadership extends its operating system into realms previously untrod by others," he says. For instance, "UNIX has no plug-and-play equivalent," says Butler, whose own company has worked to integrate new functions into traditional core processing. In other words, to create open systems. "New approaches bring new capabilities and new threats. I would be surprised if a year went by without a revelation about Windows security holes," Butler says. But others expressed more alarm. "Any complex software system . will have vulnerabilities. The surprising thing about the UPnP announcement is that it was discovered so quickly and that it was so severe," says Dr. Markus DeShon, director of security research at SecureWorks (www.secureworks.com), an Atlanta-based Internet security firm. He says Microsoft's claim that XP would be its most secure operating system to date has been based primarily on the integration of a personal firewall. "As Nimda and Code Red have shown, a firewall does not security make," says DeShon, a doctorate in nuclear physics from Georgia Tech who specializes in analyzing hacker attacks. DeShon says his company's network-based appliance, called the iSensor, blocks UPnP attacks even if it is enabled, but that "we would certainly recommend disabling UPnP in any case, and certainly by anyone whose network is not similarly protected." Gartner, the high-tech analyst and consulting firm, says security problems with UPnP and Internet Explorer 6, the software browser that also is embedded in XP, "earn a `high risk' mark on our Internet Vulnerability Risk Rating System," and it adds this stark warning: "We predict that by the end of the first quarter of 2002, standard hacker attack tools will incorporate these weaknesses into the rampant hacker scanning that is seen on cable modem and DSL Internet access systems."</p>