In keeping with its monthly patch schedule, Microsoft on Thursday said that it expects to release eight security patches next week on April 14.

Five of the patches address vulnerabilities designated "critical," two are "moderate," and one is "important."

Microsoft usually issues its patches around 10 a.m. Pacific time on the second Tuesday of the month, a day commonly referred to by Windows IT administrators as "Patch Tuesday." On the following day, the company plans to host a Webcast at 11 a.m. Pacific time to answer customer questions about the patches.

Microsoft didn't disclose the specific vulnerabilities, but said that five of them affect Windows, one affects Internet Explorer, one affects Excel, and one affects ISA Server.

The company's most recent software is affected by fewer of these flaws than its older software. Windows Vista, for example, isn't affected by two out of the five Windows vulnerabilities. And Microsoft Internet Explorer 8 isn't affected by the vulnerabilities that affect earlier versions of IE. This appears to support Microsoft's claim that its internal security procedures are making its software more secure.

On Feb. 24, Microsoft issued a security advisory that warned about a critical Excel vulnerability. It didn't fix the flaw during its March patch cycle. So presumably the Excel patch addresses that vulnerability. Exploits targeting the Excel vulnerability have been detected in the wild.

A more recent security advisory about a vulnerability in Microsoft Office PowerPoint was issued about a week ago. The flaw affects versions of Office before Office 2007. Though exploits targeting this vulnerability have been detected, it appears that a PowerPoint fix won't be delivered this month.

2009 marks the 12th year that InformationWeek will be monitoring changes in security practices through our annual research survey. All who complete the survey and provide their contact information will be entered into our prize drawing for a 46-inch Sony Bravia V Series LCD flat-panel HDTV, valued at $1,799.99. Find out more, and take part by April 26.