Microsoft’s newest computer operating system has survived its first few weeks on the market without needing any security fixes. Microsoft plugged several security holes Tuesday, but none are aimed at Windows 7, which was released Oct. 22. That’s to be expected, said Ben Greenbaum, a researcher at the antivirus software company Symantec. “Attackers will take more time to figure out ways of breaking into Windows 7,” he said. Computer users can get the patches through Microsoft’s automatic-update service.