IT administrators may find themselves grappling with triskaidekaphobia on Tuesday when Microsoft releases a flood of 13 new security patches, including several critical updates.

The release, part of Microsoft's regularly scheduled monthly security update, is the company's biggest patch roundup in months. Included will be nine Windows updates, with at least one rated critical. Also in the update bundle will be a moderate-risk update for Microsoft's SharePoint Services and Office; a .Net framework update rated "important"; a critical update affecting Office and Visual Studio; and a critical update affecting Windows, Windows Media Player and MSN Messenger.

Microsoft announced the number of planned patches in a security bulletin advance notification message posted to its TechNet website. The company has adopted a schedule of releasing security patches in batches on the second Tuesday of each month.

Details on this month's patches will be available when they are released on Tuesday. Microsoft will host a webcast at 11 a.m. Pacific Time Wednesday to outline technical details of the updates, followed by a question-and-answer session. This month's webcast has been extended by an hour to allow extra question-and-answer time.