The Microsoft® Security Intelligence Report (SIR) focuses on software vulnerabilities, software vulnerability exploits, malicious and potentially unwanted software, and security breaches. Past reports and related resources are available for download. We hope you find the data, insights, and guidance provided in this report useful in helping them protect their organizations, software, and users.

Reporting Period

This volume of the Microsoft Security Intelligence Report focuses on the first and second quarters of 2011, with trend data for the last several years presented on a quarterly basis. Because vulnerability disclosures can be highly inconsistent from quarter to quarter and often occur disproportionately at certain times of the year, statistics about vulnerability disclosures are presented on a half-yearly basis, as in previous volumes of the report.

Throughout the report, half-yearly and quarterly time periods are referenced using the nHyy or nQyy formats, respectively, where yy indicates the calendar year and n indicates the half or quarter. For example, 1H11 represents the first half of 2011 (January 1 through June 30), and 2Q11 represents the second quarter of 2011 (April 1 through June 30). To avoid confusion, please pay attention to the reporting period or periods being referenced when considering the statistics in this report.


This report uses the Microsoft Malware Protection Center (MMPC) naming standard for families and variants of malware and potentially unwanted software. For information about this standard, see “Microsoft Malware Protection Center Naming Standard” on the MMPC website.



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