Microsoft has released six security fixes, half of them rated "critical" yesterday. The patches were released as part of the company's monthly patch Tuesday.
The critical holes allow hackers to remotely take control of a PC. The first is a vulnerability in Excel which allows hackers to take over the computer if a user runs a faked spreadsheet.
The second hole is in the .NET Framework behind Vista, Windows XP, Windows 2000 and Windows Server 2003.
The third critical update is intended to prevent attacks on Windows 2000 Server and Windows Server 2003.
More details can be found at the Microsoft site here.