Microsoft announced Thursday it will deliver seven security updates next week, four of them rated “critical,” to patch Internet Explorer (IE), Windows, Office, SharePoint Server and the Silverlight media software.

March’s Patch Tuesday collection will be significantly smaller than last month’s, when Microsoft issued a dozen updates that patched a near-record 57 vulnerabilities.

Microsoft averaged close to eight updates monthly throughout 2012, said Andrew Storms, director of security operations at nCircle Security, and the count thus far this year — 8 in January, 12 in February, 7 in March—is close, with a slightly higher average of 9.

Four of the updates will be ranked critical, Microsoft’s highest threat rating, while the remainder will be labeled “important,” the next step below critical.

The most notable of the seven, pegged today as “Bulletin 1,” will affect all versions of IE, ranging from the 12-year-old IE6 to the just-released IE10 on Windows 8 and Windows RT.

IE10 on Windows 7, which started appearing on PCs powered by that OS just last week, will not be patched, indicating that Microsoft fixed the flaws there on the fly.