SAN FRANCISCO - Microsoft Corp. plans to issue a dozen security alerts on Tuesday -- some carrying the highest risk rating of critical -- as part of a monthly security update to fix flaws in its software.
Nine of the patches relate to its Windows operating system, two address problems in its Microsoft Office productivity software and the other is for the company's Exchange e-mail server software, Microsoft said on its Web site.
Microsoft, which makes the Windows operating system that runs on 90 percent of the world's computers, will issue patches to fix the problems as part of its monthly security bulletin.
The world's biggest software maker defines a flaw as "critical" when the vulnerability could allow a damaging Internet worm to replicate without the user doing anything to the machine.
Microsoft's Exchange software allows users to send and receive e-mail along with other forms of communication through computer networks.
The company has been working for more than three years to improve the security and reliability of its software as more and more malicious software targets weaknesses in Windows and other Microsoft software programs.
Microsoft makes the patches available for download at www.microsoft.com/security .
