Microsoft is planning a major raft of security fixes this month in its monthly Patch Tuesday update.

The update will occur on Wednesday, NZ time, addressing 25problems, five of the vulnerabilities being rated Critical. Some apply to enterprise applications including Microsoft Office and Exchange. Affected operating systems include Windows 2000, XP, Vista, 2003, 2008 and Windows 7.

The critical flaws could allow a remote attacker to take control of a machine, install malicious software, or contribute to a denial-of-service attack.

The fixes will be delivered via automatic updates and most will require the user to restart their computer.