Patch Tuesday has arrived, officially introducing three "Critical," four "Important" and three "Moderate" rated security bulletins from Microsoft. Eight of the bulletins pertain to Windows with the remaining vulnerabilities affecting Exchange, ISA Server and Windows Services for Unix.

The three bulletins that are labeled as being Critical, the most severe designation, detail vulnerabilities that allow malicious users to take complete control over Windows.

Tuesday's disclosure of the security flaws in its products is the most voluminous of any month since February, when Microsoft released a total of 12 fixes to address flaws in SharePoint, Microsoft's .NET Framework, Office and Windows Media Player.

Since that time there were no bulletins released in March; eight in April, five of those being considered to be Critical; and one Important bulletin in May.

Tuesday also marks the debut performance of Microsoft Update as Microsoft's primary channel for the distribution of patches. Microsoft Update unifies patching for Windows and Office, providing customers with performance and security updates via the company's "Update Services" platform.

Customers may protect themselves by enabling Automatic Updates in Windows, or by visiting Microsoft Update directly.