The growing popularity of Linux -- an open-code software that is freely available on the Internet and easily modified by users -- is a threat to the global dominance of Microsoft's Windows.
Linux violates more than 228 patents, according to a recent report from a research group, Microsoft Chief Executive Steve Ballmer said at the company's Asian Government Leaders Forum in Singapore.
"Someday, for all countries that are entering the WTO (World Trade Organization), somebody will come and look for money owing to the rights for that intellectual property," he added.
The Open Source Risk Management Group said earlier this year that potential intellectual property claims against Linux could expose users to unexpected claims that might result in lawsuits.
Software developer SCO Group Inc. , which claims that Linux is based on its Unix software, is suing companies including International Business Machines Corp.
Singapore's Ministry of Defense last month switched 20,000 personal computers to run on open-source software instead of the Microsoft operating platform.
Other governments in the region are also looking to use more open-source software. China, Japan and South Korea this year agreed to jointly develop applications running on Linux.
At a conference in Milan later on Thursday, Microsoft Chairman Bill Gates avoided a direct answer when asked whether he was worried about competition from Linux.
"In the market where Microsoft is, there's a lot of competition," he said. "We compete with Unix and we're doing very well because the Windows (market) share has increased every year. It's out there; it's something we compete against."
The Chinese government, in particular, sees its reliance on Microsoft as a potential threat. Conspiracy buffs believe certain patches in the Windows code might give U.S. authorities the power to access Chinese networks and disable them, possibly during a war over Taiwan.
Ballmer said the security fears some governments had about using Microsoft software were overblown.
"We think our software is far more secure than open-source software. It is more secure because we stand behind it, we fixed it, because we built it. Nobody ever knows who built open-source software," he added.