Linux software can now officially be used on the most sensitive computers in corporations and government.
This follows the Common Criteria organisation, an international technology standards body, certifying Linux for 'mission critical' computers.
The certification means that Linux, a top rival to Microsoft Corp, can be used inside banks, the Pentagon and top US government agencies, including the CIA.
The certification also means that Linux can be used on computers that deliver ammunition, food and fuel to soldiers, an agency report said.
The certification is akin to the technology industry's seal of approval.
The stamp of approval may help persuade governments and corporations to consider Linux, created and developed collectively by an international community of programmers, as an alternative to Microsoft's flagship Windows software.
Linux was certified as providing only 'low to moderate' security, compared with the same group's certification as 'moderate to high' last year of the security of Microsoft's Windows 2000 software. Linux software, whose popular mascot is a penguin, was under testing for better-security ratings.
The approval, however, involves only one version of Linux, from SuSE Linux AG, a vendor based in Nuremberg, Germany, when the software is installed on a particular line of IBM's server computers. IBM, which paid roughly $500,000 for the testing, and SuSE (pronounced 'SOOS-ah') were announcing the certification jointly.